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A failed disk in a jet engine turbine sparked a fire on a jet that was taking off at Chicago’s O’Hare Airport Friday, forcing the evacuation of passengers on emergency slides, the National Transportation Safety Board said Saturday.

Twenty people who suffered minor injuries while evacuating the American Airlines Boeing 767-300, which suffered an "uncontained engine failure" while taking off bound for Miami at around 2:30 p.m. local time (3:30 p.m. ET), were released by Saturday, NTSB senior investigator in charge Lorenda Ward said.

"As a result of the uncontained engine failure a fuel pool fire erupted under the right wing," she said. The stage 2 disk of the high pressure turbine failed, she said.

One part of the disk was found at a UPS warehouse more than 2,900 feet to the south, and another piece was found nearly 1,600 feet to the north on airport property, she said.

The plane stopped with 3,000 feet of runway remaining, Ward said. "That's a lot of runway to have left to you" she said. Passengers described a loud boom and the aircraft veering to the side, with those on board screaming.

The fire never breached the inside of the cabin but smoke did enter the cabin, Ward said. There were 161 passengers and 9 crew members on board. The NTSB will review maintenance records, and the incident is still under investigation, Ward said.