Metro said it has undertaken corrective action on several safety issues highlighted in a critical federal report released last month, but it failed to follow the proper procedure for doing so, a top federal transit official said Thursday.

“I appreciate the commitment to these issues and addressing them quickly, but I want to underscore that the safety directive requires FTA approval of all corrective actions,” Therese McMillan, acting administrator of the Federal Transit Administration, told the Metro board. “FTA has not approved any of the actions listed by [the Washington Metropolitan Area Transit Authority] . . . and therefore none can be considered final.”

McMillan’s remarks to the board came a little more than a month after a 116-page FTA Safety Management Inspection highlighted 91 corrective actions Metro needs to take for its rail and bus operations. Metro submitted a preliminary response to the report July 13, but aspects of it will need to be reexamined for the final report that is due in mid-September.

The unprecedented federal review found significant flaws in Metro’s safety-management system, particularly in its central train control center, which is responsible for monitoring the movement of trains through the system, similar to air traffic controllers monitoring flights.

The report said the center is chronically understaffed, chaotic and filled with distractions. It also said its workers lack adequate training and have no formal checklists to guide them in doing their jobs. Employees frequently ignore rules, such as not using cellphones while on duty. And, in some instances during the review, miscommunication led to trains being directed into areas that should have been off-limits.

It listed 78 corrective actions for the Metrorail system and 13 for Metrobus.

Metro’s response, McMillan said, indicated that several corrective actions were underway or would begin. But the FTA is the only body that can approve such actions.

FTA staff were scheduled to meet with Metro officials Friday to discuss the steps that must be taken to draft a final plan addressing all 91 corrective actions.

“It will not be sufficient to simply assert that an action currently underway or soon to be initiated satisfies the requirement of the safety directive,” McMillan said. “In particular, corrective actions developed for other problems or implemented before the FTA safety report was even issued may not be an appropriate solution.”

New authority granted by Congress in 2012 allows the FTA to oversee and provide recommendations for Metro operations but does not allow it to impose fines for failing to adhere to them.

The beleaguered transit system’s woes also have captured the attention of Cabinet officials. Last week, Transportation Secretary Anthony Foxx convened a meeting with top elected officials of Virginia, Maryland and the District to discuss what he termed the “urgent safety issues” plaguing the system.

On Thursday, McMillan declined to disclose details of the discussion, calling it a private meeting. But the changes Metro needs, she said, would require more than minor modifications to “business as usual.”

Metro board members were invited to ask questions of the transit chief after she offered a prepared statement. Board member Michael Goldman asked McMillan about the safety of the Metro system as a whole.

Metro is “not unsafe,” McMillan had said last month in response to the report’s release, and she reiterated that sentiment Thursday.

“I take WMATA every day,” she said. “The important observation is there are steps to make WMATA safer. And that is what we intend to do.”

Goldman thanked McMillan for her response, calling it a “vote of some confidence, anyway.”

“What was striking was her emphasis on Metro safety programs, on what she felt weren’t being followed,” Goldman said after the meeting. “There’s a lot of areas that need improvement.”

In her opening statement, McMillan had criticized Metro for failing to comply with its own safety protocols. She said its employees were ill-equipped to respond to emergencies and that the time slots available to perform necessary track maintenance are shrinking.

She urged swift and sweeping changes in the agency’s operations.

After McMillan’s remarks, board members sought clarification from Metro executives as to how the changes would be addressed. The Metro board’s chairman, Mortimer L. Downey, addressed Jack Requa, Metro’s interim general manager, directly.

“Metrics and actual achievement results have to be a part of this process,” Downey said. “They will be looking for actions that have been taken, not simply plans.”

Requa said the issues McMillan alluded to would be addressed in a timely fashion.

“We’re going to continue prioritizing the work that we need to get done,” he said. “Safety comes first.”

Requa said he did not think that Metro employees are facing shrinking windows to perform necessary track work and maintenance, as McMillan said.

“We think that we are assigning the appropriate amount of time with the people, the materials that we have,” he said. “We’ll have that discussion with the FTA, and we’ll come to a conclusion as to whether we need to take further actions.”