The obstruction was first reported around 12:45 p.m. between the West Oakland and 12th Street stations, BART spokesman Chris Filippi said.
Trains were turning around in the East Bay and in San Francisco instead of crossing the Bay, but as of shortly after 1:30 p.m. service was resuming after crews cleared the downed line, Filippi said.
He said riders could expect residual delays while BART gets back to its normal service.