CHICAGO — For the second time this week, a Southwest Airlines plane has aborted a takeoff at Chicago’s Midway International Airport. 

Federal Aviation Administration spokeswoman Elizabeth Isham Cory said the crew reported an engine problem Friday and the FAA will investigate.

Southwest said the Philadelphia-bound plane with 136 passengers returned to the gate after the pilot of another Southwest aircraft saw “potential signs of a mechanical issue.” Spokeswoman Emily Samuels said an initial review found nothing wrong but the aircraft remains in maintenance.

On Wednesday night, a Southwest plane headed to Boston from Midway cut short its takeoff because of a mechanical issue. The Fire Department said one of that plane’s engines caught fire.

In another incident at Midway, ground equipment struck a Southwest plane and a jet bridge Thursday. No one was injured.