At least two people are receiving medical treatment after a fire was reported Thursday afternoon in the trolley system connecting the Rayburn House and U.S. Capitol buildings.

The D.C. Fire and EMS Department confirmed crews responded to a small electrical fire atop the underground trolley, which was later extinguished. 

At least two patients are being medically evaluated, according to D.C. Fire.

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None of the passengers on the trolley were injured, officials said.

It is unclear who was in the vehicle at the time of the incident.

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Fire personnel are assessing smoke conditions, as of 5:10 p.m. local time.

The Metropolitan Police Department said Independence Avenue is closed in both directions between Washington Avenue, SW and Second Street, SE. 

“Use alternate routes to avoid this area,” police wrote in a social media post.

The cause of the fire has not yet been released.

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The U.S. Capitol subway system is used to move lawmakers, aides and high-profile guests safely between government buildings.

Its three lines are operated and maintained by the Architect of the Capitol (AOC).

This is a developing story. Please check back for updates