CHICAGO (CBS) — CTA Blue Line service was suspended between O’Hare and Jefferson Park Tuesday afternoon, due to what the agency called a “track condition.”

The suspension of service was later scaled back to between Jefferson Park and Cumberland, with trains skipping Harlem.

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The CTA did not immediately confirm reports that a train malfunction was to blame for the suspension or that a train was evacuated.

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Shuttle buses were made available. Other alternatives such as buses, or buses to other rail lines, were also advised.

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Meanwhile, Blue Line trains were also running with delays after an unauthorized person got onto the tracks at the Damen stop in Wicker Park.