Updated at 8:31 a.m.

Metro said it does not know what caused smoke Thursday morning at the Virginia Square station.

Arlington firefighters at the scene found smoke in the tunnel between the Clarendon and Ballston stops. The Virginia Square station was evacuated and service on part of the Orange and Silver lines was halted for nearly two hours.

Metro said the cause of the incident is under investigation.

Riders shared ā€”

Updated at 7:54 a.m.

Metro said service is back on the Orange and Silver lines between the East Falls Church and Clarendon stops.

There were no immediate details as to what caused the earlier smoke incident at the Virginia Square stop.

Updated at 7:43 a.m.

Metro said service remains suspended on part of the Orange and Silver lines between the East Falls Church and Clarendon stops. They said there is a track problem at the Virginia Square stop.

Earlier, Arlington firefighters came to the Virginia Square stop after smoke in the ā€œstation and tunnelsā€ between the Clarendon and Ballston stops.

It was not clear how long they will last.

Updated at 6:58 a.m.

Arlington Fire officials said Metro is ā€œworking to reopenā€ the Virginia Square station after smoke was found in the tunnel between the Clarendon and Ballston stops.

The problem has caused delays on the Silver and Orange lines and no trainsĀ wereĀ running between the East Falls Church and Clarendon stops. Fire crews were on the scene.

It was not known if anyone was hurt.

Firefighters were trying to figure out the cause of the smoke. The Virginia Square stop had to be evacuated.

Buses are being sent for riders. The problem is also causing delays on the Blue Line.

Original post at 6:25 a.m.

Metro trains were not running along parts of the Orange and Silver lines in Northern Virginia after smoke was reported at the Virginia Square stop.

Trains were not running between the Ballston and Clarendon stops.

Arlington Fire officials said on Twitter that crews were on the scene for ā€œsmoke in the tunnelā€ at the Virginia Square stop. The station, fire officials said, was being evacuated.

It was not immediately known if anyone was hurt.