Service is beginning to return to normal after an N-Judah train derailed at the Church and Duboce streets intersection before going underground Thursday evening.

What caused the train to derail is unknown, but the San Francisco Municipal Transit Agency is investigating the incident, according to agency spokesman Paul Rose.

The train, which was heading toward downtown, derailed around 7:15 p.m. Shuttle buses were in place, but as of 8:20 p.m., light rail service is returning to the tracks.

Rose said no passengers were injured and there still may be residual delays.

“Schedules are returning to normal,” Rose said.

akoskey@sfexaminer.com