CHICAGO (CBS) — CTA Red Line trains were rerouted to the elevated lines between the Fullerton and Cermak-Chinatown stops Sunday night due to an “unauthorized person” on the tracks at Grand.

Trains will stop at Armitage, Sedgwick, Chicago Avenue, the Merchandise Mart, Clark/Lake, State/Lake, Washington/Wabash, Adams/Wabash, and the elevated Roosevelt stop.

The Chicago Transit Authority also advised using buses as an alternative.

The CTA did not provide further information about the unauthorized person.