The U.S. Park Police has lost track of thousands of handguns, rifles and machine guns in what a government watchdog agency concluded is the latest example of mismanagement on a police force trusted to protect millions of visitors to the city’s iconic monuments.

There is no indication that police guns got into the hands of criminals, but the Office of the Inspector General for the U.S. Department of the Interior warned that the Park Police might not know if they had. In a scathing report, the authors said there is “credible evidence of conditions that would allow for theft and misuse of firearms, and the ability to conceal the fact if weapons were missing.”

The probe was launched in part because of an anonymous tip that Park Police officers were improperly taking weapons home. Investigators discovered two instances in which that had occurred, but they found many other troubling examples of mismanagement, according to the report.

Investigators found 1,400 guns that were supposed to have been destroyed or melted down. An additional 198 handguns donated by the Bureau of Alcohol, Tobacco, Firearms and Explosives are sitting in a building in Anacostia but don’t show up in official records.

In another instance, the agency in October 2011 sent a list of 18 pistols, shotguns and rifles it described as lost or stolen to a national database. But it never launched an internal investigation. The guns, it turned out, had been destroyed or given to other agencies — or they were still in Park Police possession, according to the report. One Remington shotgun remains missing.

The Park Police report from the Office of the Inspector General.

“Commanders up to and including the chief of police have a lackadaisical attitude toward firearms management,” wrote Mary L. Kendall, the deputy inspector general. “Historical evidence indicates that the indifference is a product of years of inattention to administrative detail.”

Investigators took an unusually harsh tone in part because they said similar problems found in 2008 and 2009 were never fixed — a symptom of “the decade-long theme of inaction and indifference” of top Park Police managers. The Washington Post obtained an advance copy of the report.

It’s unclear how long the agency has not been keeping track of its weapons, but one example in the report documents how a former police chief’s gun was missing for a decade and no one knew.

The report does not spare the current chief, Teresa Chambers, who returned to her post in 2011 after she was suspended and then fired eight years earlier for criticizing staffing levels in a Washington Post article. The investigators accused Chambers and her staff of harboring a “lackadaisical attitude” but also noted that top commanders frequently gave her wrong or outdated data, which she relied on in signing off on gun inventory reports.

A Park Police spokesman did not return calls seeking comment, and Chambers was not available. Jeffrey Olson, a spokesman for the National Park Service, which oversees the Park Police, said Chambers has been ordered to implement the inspector general’s recommendations “without delay,” including an immediate weapons inventory.

“I have no tolerance for this management failure,” Park Service Director Jonathan B. Jarvis said in a statement. “The safety and security of our visitors and employees remain our highest priority.”

Problems uncovered by the inspector general include two officers who took guns home without permission, including a semiautomatic rifle present during the presidential inauguration in January. The report also found that a former chief kept his department-issued sidearm for 10 years after retirement without anyone noticing.

Investigators concluded that the Park Police not only can’t keep track of the guns it has but it hasn’t disposed of guns more suited for collectors than lawmen. The agency still has 20 M1 Garand rifles, the standard field gun in World War II, and four Prohibition-era tommy guns. The inspector general noted that these weapons are of “limited” use.

The Park Police has about 600 officers deployed primarily in Washington, New York City and San Francisco. They patrol Park Service property, including the Mall and many of the District’s national monuments and parkland. Their jurisdiction includes vast areas of downtown Washington and some of the busiest tourist attractions in the country.

Five years ago, the inspector general chastised the agency for failing to “adequately perform” its two stated missions — functioning as an urban police department while protecting national heritage centers. The review found officers to have low morale, lack of confidence in command and an inability to keep its fiscal affairs in order.

In the latest report, investigators tried to examine allegations that the Park Police could not account for a cache of military-style rifles, that inventories were incomplete and that some guns had been taken by officers for personal use. But the task was difficult, according to the report, because staff from the chief down to officers “had no clear idea of how many weapons they maintained due to incomplete and poorly managed inventory controls.”

Park Police guns turned up in odd places. In 2011, former police chief Robert Langston, who retired in 2001, showed up at a firearms qualification course for former law enforcement officers, according to the report. Running the course was a former Park Police officer who had been a member of the department’s special weapons and tactics team. He also was an inspector general in the U.S. Department of Housing and Urban Development.

The official noticed that Langston’s handgun belonged to the Park Police, the report said. He seized the weapon and returned it to the agency. Current Park Police officials could not explain how the former chief kept his gun, which was “unaccounted for on inventories that followed his retirement,” according to the report.

Langston did not return a phone call seeking comment.