Metra service was restored after trains were halted on the BNSF Railway near Congress Park in Brookfield Monday afternoon due to potentially hazardous material near the tracks.
"Trains may incur extensive delays enroute and please listen to platform announcements for the location of your trains," Metra said on its website. "We will continue to provide updated information as it is received."
BNSF Railway riders had been advised to use alternate transportation, such as the Union Pacific West, Milwaukee West and Rock Island District.
All other lines to and from Chicago Union Station were operating normally, but may have experienced overcrowding due to the delays.
The delay could still impact rush-hour commuters and fans heading to Wrigley Field for Monday night's Cubs playoff game against the St. Louis Cardinals.