WASHINGTON (WJZ) — More unanswered questions after the shutdown of D.C.’s Metro system, impacting the commute of tens of thousands of area workers.

Inspectors admit finding conditions so dangerous, they would not run a train over them. But what’s causing those conditions is still unknown.

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Meghan McCorkell has more on the investigation.

Thousands of Marylanders ride the D.C. Metro every day and the state pays hundreds of millions to the system, but safety concerns still linger.

Dozens of passengers trapped inside a smoke-filled Metro tunnel; almost 100 people injured and one woman killed.

Metro officials now say a tunnel fire on Monday had striking similarities to the fatal fire last year, and that caused them to shut down the entire system.

Inspections uncovered some disturbing discoveries–dozens of frayed, damaged electric cables–26 defects found in all across the 91 rail stations. Some so dangerous…

“With a frayed cable like that we would not run a train over it, we would have stopped it immediately,” said Paul Wiedefeld, WMATA general manager.

What Metro officials still can’t answer–what is causing these cables to deteriorate? The cables were inspected in June.

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“Like most of our infrastructure in this country, we tend to take it for granted until it’s suddenly not there,” said Casey Dinges, American Society of Civil Engineers.

More than 700,000 people ride the D.C. Metro every day; hundreds of thousands of them are from Maryland.

Casey Dinges with the American Society of Civil Engineers says the safety issues come down to money.

“The fundamental problem we’re having here is a lack of investment,” he said.

Maryland contributed $450 million to Metro’s budget for 2016. Still, Metro officials say they hope the shutdown is a wake up call about what more is needed.

“We need to invest in our system once and for all. We need to establish the dedicated funding source,” said Jack Evans, Metro chair.

As more and more riders take to the rails.

Several lawmakers are now calling on Congress to step up funding for the D.C. Metro.

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The Federal Transit Administration is now temporarily responsible for safety oversight on the rail system.