BART police say the central power system went down, leaving train controllers unable to communicate with train operators.
BART says it had to shut down all service throughout the Bay Area at 9:18 a.m. due to safety concerns.
The move left many passengers stuck on trains. "Two hours I've been waiting trying to get to Oakland. It's not cool. It's not cool," one passenger said.
BART's technicians continue to investigate the cause of the power system failure.