CHICAGO (AP) -- Two passenger jets began to take off at the same time on intersecting runways at Chicago's Midway International Airport, prompting a controller to shout over the radio for one of the pilots to halt to avoid a collision, aviation officials said Wednesday.

The Federal Aviation Administration was investigating Tuesday night's near miss in which each plane stopped about 2,000 feet from the runway intersection.

Southwest Airlines Flight 3828 to Tulsa, Oklahoma, had been cleared for takeoff and was speeding down the runway. At the same time, an air traffic controller saw Delta Air Lines Flight 1328 to Atlanta beginning to take off on the intersecting runway without proper clearance, the FAA said.

"1328, stop, stop stop!" the controller shouted, according to audio posted on the website LiveATC.net.

"1328 stopping," the pilot answered in a clam voice, before the controller directed both planes to different taxiways.

The Southwest plane also safely aborted its takeoff, said airline spokesman Brian Parrish. The aircraft later continued on to Tulsa.

Delta spokesman Morgan Durrant said the airline was cooperating with the investigation but that he could not provide any information on what might have led to the runway mix-up.

In the air traffic audio, the controller tells the pilots that they keep answering for each other, suggesting confusion.

The Southwest pilot later asked whether his aircraft was the one cleared for takeoff.

"Yes sir, you were," the controller responded. "You were the one. You were doing what you were supposed to be doing."