Metro issued a rare apology Friday for two back-to-back track fires that brought the morning commute to a grinding halt. The Tweet also blamed issues on “water infiltration into the tunnels.”

Yes, water causes fires on Metro. Specifically a nine mile stretch of the red line north of Dupont Circle that was mined before the advent of modern tunneling techniques. The issues are detailed in a 2004 U.S. Geological Survey report obtained by WUSA9.

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The report says the tunnels were bored in the 1980s “when no proven water-sealing technologies were available to effectively mitigate water intrusion by sealing the tunnel walls.”

But that’s a big problem for Metrorail. Trains are powered by the 750-volt third rail. The water can cause an electrical arc which sometimes leads to fire.

Tracks are more than a hundred feet underground in some places and surrounded by groundwater. Metro workers regularly patch leaks and install gutters but sometimes—including this latest time—it is not enough.

Ashley tweeted "Hey Metro - when my fare goes up in 2 days, are these amazing 2 and a half hour commutes included?"

Metro also points to rain that fell in the early morning. WUSA9 counted only about a tenth of an inch of rain. WMATA says it’s the speed in which the rain came down.