Regular service has resumed on the A, C, and D subway lines after they were disrupted by a train derailment on the Upper West Side on Saturday, but Metropolitan Transportation Authority officials say riders can expect residual delays.

The last car of a downtown A train went off the tracks at the 81st Street station around 10 a.m. Saturday.

Fire department officials say no one was hurt and passengers were transferred to another train.

The derailment is under investigation.

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