A preliminary investigation blamed a bird strike for forcing a United Airlines (search) flight bound for Brazil to make an emergency landing at O'Hare International Airport (search) shortly after leaving the airfield, a United spokesman said Monday.

The incident marks the second time in a month an airplane has been forced to make an emergency landing at O'Hare after a bird was sucked into the engine.

"All signs tell us it was a bird strike," United spokesman Jeff Green said. He said feathers were found in the engine as soon as the plane landed Sunday night.

None of the 179 passengers and 12 crew members aboard the Boeing 767 (search) were injured, and Green said that all the passengers were on their way to Sao Paolo aboard another plane Monday.

According to the Federal Aviation Administration (search), the plane's crew reported a problem with one of the engines shortly after its departure from O'Hare about 9:50 p.m. Sunday.

The pilot reported "a compressor stall, something that caused flames to shoot out from the engine," according to the FAA.

Green said the pilot noticed the problem almost immediately after takeoff and shut the engine down. The pilot continued to fly over Lake Michigan, where fuel was dumped, and then returned to O'Hare. He said the two-engine planes are capable of flying with one engine.

The Elk Grove Village Fire Department said residents of the suburban Chicago community called 911 and reported seeing flames coming from the plane.

Elk Grove Village Fire Capt. Scott Miller said some of the firefighters heard a series of "explosions or concussions" from inside their station, which is near O'Hare.

"We went out in front of station and we observed the plane circling the community," Miller said. "We thought we had observed a bit of flames coming out from one of the wings."

An investigation of a Sept. 16 emergency landing by an American Airlines (search) flight bound for Philadelphia from Chicago determined that six double-crested cormorants had been sucked into one of the engines, causing severe damage. None of the 112 people aboard that plane were injured.