BART service was fully restored at 10:50 a.m. on Saturday after a computer problem shut down the entire system for hours.

The closure was first announced at 5:42 a.m., with limited service restored at around 9 a.m. A "bus bridge" was established between Daly City and Millbrae since there was no service beyond Colma to SFO.

BART originally said that crews working overnight on the system's uninterruptible power supply in Oakland "ran into problems" that impacted the traction power supply system and train control routing system. The traction power system sends power to the trains and the routing system is how BART programs "which direction and route the trains should maneuver."

However, BART now says that they no longer believe the overnight maintenance caused the computer issue.

"While we originally believed this was caused by planned maintenance work to our uninterruptible power supply system, we have now determined this work did not cause the network failure," the agency said in a press release.

BART said it will perform a forensic evaluation to determine the cause of the network failure. This will take several days due to the complexities of the system, the press release stated.

BART encouraged travelers affected by the outage to use its trip planner to book alternative means transportation.

In addition, bus agencies that serve BART stations offered to let riders affected by the outage to ride for free.

Eric Ting is an SFGATE staff writer. Email him at eting@sfchronicle.com and follow him on Twitter

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