Blue Line service was suspended near O'Hare International Airport for about an hour Tuesday morning due to "Fire Department activity," according to the CTA.
Service was restored and trains were running as of 7:20 a.m. Stops between O'Hare and Rosemont had been affected, with trains running only between Forest Park and Rosemont, the CTA said in an alert.
The Chicago Fire Department didn't immediately respond to questions about the activity.
Shuttle buses were made available between the affected stops, the CTA said.
