SAN FRANCISCO (KCBS) — The San Francisco Municipal Transit Agency is investigating the derailment of a Muni streetcar in front of the West Portal Station early Friday morning.

The incident happened about 5:30 a.m. when an inbound L Taraval train’s wheels came off the track as it approached Ullola Street—right in front of the entrance to the West Portal tunnel.

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The problem, officials on the scene said, may have been caused by a switch signal which hangs above the street—the switch controls which way the wheels should turn.

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No passenger injuries were reported.

While the light-rail service was restored within an hour, the schedule was off. A Muni supervisor said they were going to keep bus shuttles in service though the commute to alleviate pressure for the inbound line.

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