By CBS 2 Chicago Staff

CHICAGO (CBS) — A CTA Blue Line train derailed on the Northwest Side early Saturday morning after what officials call a switching error.

Around 1:30 a.m., the first car derailed near Montrose right in the middle of the Kennedy.

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First responders helped escort passengers off the train. Chicago police said 25 people were board. Four of them were treated for minor injuries, according to the Chicago Fire Department.

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Some lanes were closed on the Kennedy for emergency vehicles, but by 5 a.m. only one lane in each direction was closed due to the incident.

Shuttle buses were taking Blue Line passengers between Belmont and Harlem until that service is back up and running.

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CBS 2 Chicago Staff