A BART maintenance truck derailed early Thursday morning, causing delays for early commuters.
BART spokeswoman Alicia Trost said the truck derailed between the South Hayward and Union City stations about 3:30 a.m.
The transit agency is now single-tracking to get around the accident which is causing some delays, to the Fremont and Warm Springs lines.
Trost said an inspection crew discovered damage to the tracks, and there was no estimated time on when it could be repaired.
There were no injuries from the accident, but BART says service delays could get longer, as service begins ramping up during the morning commute.