REDWOOD CITY (KPIX) — A Caltrain engineer was struck by a thrown object Friday evening as the train he was operating was moving north through Redwood City, according to officials.

Caltrain officials said the incident involving train #381 happened at around 6:30 p.m. just outside the Redwood City station. It is causing major delays as officials single track trains through the area.

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It’s not known who threw it or what the object was. The train was stopped while transit police investigated.

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The train’s conductor called for an ambulance but the extent of the engineer’s injuries is not known.

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There were 450 passengers on board who were being transferred to a different northbound train to continue their journey after train #381 was terminated in Redwood City.