7:53 p.m. update: 24th Street Station is open and trains are running normally. The authorities did not determine what caused the smoke that shut down the station for over an hour.
BART's 24th Street Station is closed after a train arrived at the boarding platform billowing smoke, prompting an investigation.
"We think it may have hit something on the track prior to entering 24th Street Station but that's being investigated right now," a BART spokesperson said.
Passengers were removed from the train and platform level around 6:40 p.m. to allow BART Police Department and San Francisco Fire Department personnel to investigate.
Muni is providing additional bus service to BART passengers.
No passengers have been reported injured.