The nation’s top transportation official said Wednesday that officials at the Federal Transit Administration will open three new safety investigations into Metro’s rail operations focused on the quality of the transit agency’s track system and the behavior of its train operators.

In his appearance before the Transportation, Housing and Urban Development (THUD) Appropriations Subcommittee, where he was set to testify about his department’s budget request, Transportation Secretary Anthony Foxx addressed Wednesday’s unprecedented 24-hour shutdown of the Metro system.

“Not only is it disruptive to D.C. commuters, but it’s disruptive to the operations of the federal government,” Foxx said about the closure, which left thousands of people scrambling for alternative ways to get to work and school. Many federal workers, who were given the option of unscheduled leave or telework, opted to stay home Wednesday.

Foxx went on to express his continued frustration that officials in the District, Maryland and Virginia have failed to create a new safety oversight agency to monitor Metro’s operations despite repeated admonishments by him and other elected officials. Officials in the three jurisdictions recently signed a memorandum of understanding saying they will move forward on a plan to create a new safety agency, but said one would not be in place until at least 2017 — a development that Foxx sharply criticized.

Foxx also announced that FTA inspectors next week will begin investigating why so many of Metro’s train operators continue to run red light signals and use their emergency brakes during normal train operations. He said inspectors will take a closer look at “rail integrity” in the system. Last August, following the derailment of a Green Line train on a stretch of track near the Smithsonian Station, Metro officials acknowledged that they had known for a month that section of track was flawed. The “safety blitz” will begin next week, Foxx said.

Maryland Sen. Barbara Mikulski (D), who has been among Metro’s biggest boosters, but also one of its fiercest critics was blunt in her assessment of the transit agency.

“Today we have heartburn once again over the Washington Metro,” she said. The shutdown was drastic, disruptive — ” . . . yet I believe it was necessary,” she said.

“For months and years we’ve called for a culture of safety and what we’ve gotten is a buzz saw of resistance to safety,” Mikulski continued. “What we need is a Metro that really works in a way that people have confidence that when they get on, they’ll get off and be okay.”

Mikulski said after Congress returns from its spring break, she and other members of the region’s delegation plan to hold an oversight meeting with Metro General Manager Paul J. Wiedefeld.

“We can’t enable the continuation of these safety failures any longer,” she said.