BART riders at San Francisco stations have been experiencing major delays in the East Bay direction this morning. The cause appears to be an equipment problem that left 16th Street station filled with smoke.

Members of the Fire Department reported to 16th and Mission at around 9 a.m. this morning after the situation was reported. Per the department on Twitter, the smoke may have come from a train's brakes.

No smoke-related injuries were reported.

Update: KRON4 reports that, indeed, a train's brakes were engaged while the train was moving, causing smoke.

Responding to the smoke, one passenger activated the emergency door, exiting the train. That, the Chronicle writes, caused further delays.

The train has been taken out of service and will be inspected. The original error of engaging the brakes train was moving was not a human error according to a BART spokesperson.