The entire Washington Metro subway system could be shut down if officials don’t follow the safety measures ordered by the Transportation Department, Transportation Secretary Anthony Foxx said Tuesday.

"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."

Foxx added that officials haven’t identified the root cause of the incidents involving the electrical arcing, smoke and fire, and have no plan for how to fix the problem. DOT officials believe there might be too much electrical power flowing through the subway system, he said.

In a 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 issued a slew of safety directives over the weekend in response to the latest incident. One recommendation was to cut the number of railcars per train from eight to six, which in turn would make trains more crowded during rush hour.

The Metro handles about 700,000 riders per 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.

Meanwhile, the subway’s general manager Paul Wiedefeld met with 650 agency managers in a closed-door meeting to discuss ways to fix the safety issues.

Fox 5 DC reported that Wiedefeld urged mid-level managers and senior staff to put safety first. He introduced a new slogan: “Safety Trumps Service.” And a flyer was handed out to all managers at the end of the meeting.

The Associated Press contributed to this report.