A broken pipe near the O'Hare CTA Blue Line station emitted an ammonia-like odor Thursday morning and led to the shut down of train service to the Rosemont station for some three hours, officials said.
A hazmat crew from the Chicago Fire Department responded to the platform of the O'Hare station after 9 a.m., where a nearby pipe was leaking liquid, authorities said.
Initial reports were that crews were responding to a water leak, but a fire department official later said crews were responding to an apparent ammonia leak.
The hazmat crew determined the liquid was not a hazardous substance, according to Gregg Cunningham, a spokesman for the Chicago Department of Aviation.
CTA officials were asked by the fire department to shut down service at the O'Hare station, and the immediate area was evacuated. Cunningham said crews worked to ventilate the train platform area, which sits underground.
By 12:30 p.m., the leak had been contained, and normal Blue Line service resumed.
No one required medical attention, authorities said.
During the CTA shutdown, outbound trains stopped at the Rosemont station, and shuttle buses took passengers to and from O'Hare, according to CTA spokeswoman Lambrini Lukidis.
Cunningham said work must still be done to permanently fix the broken pipe, which is part of airport property and not the CTA's.