BART suspended service on the Red Line on Saturday morning between Richmond and Millbrae.
The transit agency said in an advisory at about 11:45 a.m. that an equipment problem on a train in West Oakland was causing major delays.
The Red Line was suspended about 45 minutes later.
The Blue Line is running between Bay Fair and Dublin/Pleasanton Stations.
The Green Line is running between the Coliseum and Berryessa.
There was no estimate for when the Red Line would be operating again.