As the Federal Emergency Management Agency heads into peak hurricane season, an internal investigation has imperiled its top official, sparking a growing backlash within the agency where career officials and even some political appointees are worried there is no proven disaster manager on hand to replace him.

FEMA Administrator William “Brock” Long is said to be resisting an effort by Homeland Security Secretary Kirstjen Nielsen to replace him over his alleged misuse of government vehicles. The feud among senior Trump administration officials surfaced publicly in recent days as FEMA and the Department of Homeland Security raced to prepare for the arrival of Hurricane Florence.

The prospect of Long’s dismissal has alarmed current and former staff at FEMA and DHS, and it has captured the attention of officials on Capitol Hill, who note that the agency’s No. 2 position has been vacant for nearly two years and that Trump’s current nominee, Peter Gaynor, still awaits Senate confirmation. Trump’s original nominee for the post, Daniel Craig, withdrew from consideration a year ago after reports surfaced that the DHS inspector general found he had falsified work and travel records while working for the George W. Bush administration.

FEMA’s third in command, Daniel Kaniewski, could take over, at least on an interim basis, if Long were to leave. But his background in policy and academia ­— and his lack of hands-on emergency management experience ­— has generated concern that an internal shake-up would unsettle the agency at the worst possible time.

This account of the power struggle and internal strife at FEMA and DHS is based on interviews with 14 current and former government officials and congressional aides. Most spoke on the condition of anonymity to offer their candid assessment of the matter.

“Who in their right mind thought this was a good idea to try to take out the FEMA administrator in the middle of a storm?” said one former top FEMA official, angry that the infighting spilled into public view with millions of Americans under threat from Florence. “Even if that’s your objective, save it for after the hurricane.”

Long, a veteran emergency manager whom staffers described as highly respected throughout the agency, is under investigation by the DHS inspector general for his use of government vehicles during weekend travel between Washington and his home in North Carolina to see his wife and young children. Investigators have surveilled Long during those trips, which were said to include other FEMA staffers, raising questions internally about his use of government resources, a senior administration official said Saturday.

The inspector general’s surveillance of Long was first reported Friday by the Wall Street Journal.

An official with knowledge of Long’s schedule said that while Long has traveled home often, the demands of his job have also meant large blocks of time away from his family. During one stretch from late August to early December — at the height of last year’s hurricane season — Long did not return to North Carolina once while traveling to Texas for Hurricane Harvey, to Puerto Rico and the Virgin Islands for Hurricane Maria, to Florida for Hurricane Irma, and to California to assess FEMA’s response to wildfires.

Long has told colleagues he has no intention of stepping down and remains focused on coordinating FEMA’s response to Florence, which has killed at least five and triggered widespread flooding in the Carolinas. At a briefing Thursday, Long denied doing anything improper, saying that’s “not part of my DNA.”

DHS and White House officials, including Chief of Staff John F. Kelly, have discussed replacing Long but decided to wait until Florence passes and the inspector general’s team completes its investigation, the senior administration official said. They acknowledge Long is highly competent and that the allegations against him present a dilemma.

In a statement, deputy White House press secretary Hogan Gidley said: “We are aware of the allegations and will review the IG Report when it is complete. However, right now the Administration is working nonstop to prepare and implement a massive federal government support effort for those impacted by hurricane Florence.”

DHS officials have said that Nielsen denies asking Long to leave and that she is “confident in the leadership at FEMA and their proven disaster management ability.”

Long has kept a low profile since news of the probe was disclosed to the media, last speaking with Trump by phone on Friday, FEMA Associate Administrator Jeff Byard told reporters during a media briefing Saturday. Asked if Long would remain in the job, Byard said: “Our administrator’s our administrator. He’s given our team very clear guidance that the focus is Florence.”

Nielsen’s alleged desire to remove Long dates back months, according to people familiar with the matter who believe the inspector general’s investigation of Long is part of Nielsen’s effort to make a change at FEMA. She and Kaniewski are close friends and onetime housemates, according to three current and former colleagues.

Current and former FEMA officials said there would be alarm within the agency if Nielsen were to install Kaniewski into the top job, if only on a temporary basis while a new permanent administrator is vetted.

Kaniewski was confirmed by the Senate unanimously in September 2017 for the role of FEMA’s deputy administrator for preparedness. His title has since changed to deputy administrator for “resilience.” In that role, he oversees areas such as insurance, preparedness and grants, according to FEMA officials.

Kaniewski holds a doctorate in public policy from George Washington University, taught as an adjunct at Georgetown University, and has worked at a university think tank, a catastrophe risk-modeling firm and a federally funded research center. Yet despite his academic pedigree and policy background, he has little experience directing disaster response.

Jessica Nalepa, a spokeswoman for FEMA, said Kanieswki is “highly regarded in the emergency management community and has been an invaluable member of the Administration’s leadership team through multiple major disasters.”

“He is currently actively involved in the agency’s response to Hurricane Florence,” she said in a statement.

The top job at FEMA has been held by an official with ample leadership experience in disaster management ever since the botched federal response to Hurricane Katrina in 2005, which left more than 1,800 dead. Legislation passed in the wake of that storm mandates that FEMA’s administrator have at least five years’ experience, though the law’s vague wording allows for that experience to come from related fields beyond crisis management.

“After Katrina, the qualification to be FEMA administrator drastically changed. No more ‘Brownies,’ ” explained a current DHS official, referring to ex-FEMA administrator Michael Brown, who became the symbol of government ineptitude when critics latched on to Bush’s now-infamous declaration amid the fallout, “Brownie, you’re doing a heck of a job.”

The bitter memories of that episode could make it difficult for a policy expert like Kaniewski to step into the top job if Long departs.

“I have a lot of confidence in his ability, but at the same time I don’t want to see anyone have to replace Brock,” said former administrator R. David Paulison, who took over FEMA in 2005 after Brown’s resignation.

But Kaniewski has a powerful advocate in Nielsen, with whom he worked as a homeland security adviser to Bush and later at George Washington University’s Center for Cyber and Homeland Security. Last year, while Nielsen served as the DHS chief of staff, she lobbied for Kaniewski’s nomination to the deputy administrator position at FEMA but was overruled, according to a congressional staffer with knowledge of the process.

A DHS official who works closely with Nielsen denied that account and said Kaniewski was always intended to be head of preparedness at FEMA, not deputy administrator.

Those who’ve worked with Long describe him as “revered” among FEMA staff and state-level disaster management officials. He was emergency management director for the state of Alabama and, before that, a FEMA regional hurricane program manager.

“It’s concerning because I don’t know that you can find many others with that level of experience,” said Mark Cooper, who has worked in disaster response for three decades and is now chief of staff for Louisiana Gov. John Bel Edwards. Cooper worked closely with Long during hurricanes Gustav and Ike in 2008, when they led response efforts for the states of Alabama and Louisiana, respectively.

“He took in thousands of our residents when not a lot of other states were willing to do that,” Cooper said. “And since he’s been at FEMA, he’s been on 24/7. There’s not a time we’ve reached out, whether on Sunday or late at night, when he’s not been responsive to us.”

Current and former FEMA officials also noted that Long has filled several key political appointee jobs with experienced emergency officials. They worry that if he is forced out, those seasoned veterans may leave with him or be replaced with less-experienced ones.

Others worry that even if Long survives, the frayed relationship with Nielsen could exacerbate existing issues between FEMA and DHS. “There’s problems baked into that relationship that predate them,” explained one FEMA staffer. “During disasters, the FEMA administrator is the principal adviser to the president. They’re the ones in front of the camera and leading the charge, even though they ostensibly report to DHS. That’s always been a source of friction.”

However, one former FEMA official said a leadership change now, even though it’s hurricane season, may have less impact than some fear. “The reality is the career folks who have been working at the agency for years could run FEMA for a while just fine,” the former official said, “but that’s only true if the political folks stay out of their way.”

Philip Rucker and Mark Berman contributed to this report.