Updated

Transportation Secretary Anthony Foxx said Tuesday he seriously considered ordering a shutdown of the entire Washington Metro subway system last week and may still do that if local officials don't follow Transportation Department safety directives.

"We have the ability to withhold (federal) funds from Metro. We have the ability to shut Metro down, and we're not afraid to use the authority we have," Foxx said told reporters. "This is serious business."

Local officials have yet to identify the root cause of incidents involving electrical arcing, smoke and fire, and so have no plan for how to fix the problem, he said.

It is clear to DOT officials who watched a video of one recent incident that there is too much electrical power flowing through the subway system, Foxx said.

In the video, recorded at the Federal Center Southwest station, there is a bright flash of electrical arcing followed by billowing smoke in the same place where moments before a train had passed through. Foxx called the video "scary."

The Federal Transit Administration, which is part of the department, issued a series of emergency safety directives to Metro officials on Saturday that included steps to reduce power throughout the rail system. One recommendation is to cut the number of railcars per train from eight to six. That would make trains far more crowded at peak hours.

The subway system is used by about 700,000 riders a day.

The directives are steps to protect safety while working on the root cause, Foxx said.

Asked what would trigger a shutdown order, Foxx said not following the safe directives and not giving DOT inspectors access to tracks and facilities, as happened for several hours last week.

"It's up to them. They have to follow the directive. They have to do it expeditiously," Foxx said.

Metro officials are working to fully implement the safety directives, said Morgan Dye, a spokesman for the Washington Metropolitan Area Transit Authority, the agency that operates Metro.

Metro officials announced a track maintenance and repair scheduled on Friday that calls for shutting down or drastically reducing service to portions of the system for days or weeks at time over the next nine months.

Foxx called the maintenance schedule "ambitious," but said the plan still doesn't address the root cause of the incidents.

"Fixing the track is one thing, but some of these (incidents) may involve power plant issues, issues that go deeper into the system," Foxx said.