SAN FRANCISCO (CBS SF) — A collision that seriously injured a wheelchair-bound woman, along with an unrelated shutdown of Muni Metro service, stranded tens of thousands of commuters in San Francisco on Monday.

All San Francisco Municipal Railway subway trains were shut down Monday evening because of an electrical signaling problem, Muni officials said.

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A transformer blew around the Van Ness station around 5:45 p.m. leading to the outage, Muni spokesman Paul Rose said. He said Muni crews were working with PG&E Monday night to restore service as quickly as possible.

SFMTA officials told CBS 5 Monday night that repairs would be completed by early Tuesday morning.

The outage is unrelated to an earlier incident where a wheelchair-bound woman was hit by an F-train near the corner of Church and Market streets. She was hospitalized with life-threatening injuries, police said.

The woman was hit by an F-Market train around 5:30 p.m. near the intersection of Church and Market streets.

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Police are still investigating whether she had leaned forward toward the train or if she fell off her wheelchair, but she was struck by the westbound train traveling on Market Street from Dolores Street to Church Street, Officer Carlos Manfredi said.

The woman was trapped under the train.

Medics, firefighters, police and SFMTA officials arrived and used a special tool to raise the train and pull her out from under it.

She was rushed to San Francisco General Hospital suffering injuries considered life-threatening, Manfredi said.

One lane of Market Street was closed while police investigated Monday night, interviewing witnesses and checking video surveillance.

The F-Market line resumed its regular route around 8:40 p.m.

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