There were multiple fractures found in the right engine according to investigators from the National Transportation Safety Board (NTSB). Authorities described it as fatigue cracking in the turbine disk.
There is still no word on why the cracking occurred but a revelation raised questions about whether other planes are at risk.
Close-up pictures obtained by the ABC 7 I-Team show the damage to the right side of the Boeing 767 that occurred when the engine blew apart.
Federal authorities said the right engine high pressure turbine disk broke into at least four pieces and some of them flung sideways a few thousand feet away.
The takeoff direction of the jetliner marked on an aerial map provided by NTSB inspectors shows a gouge in the runway believed to be where the engine started rupturing. As the plane was rolling at 147 miles an hour, tire marks show where it started braking.
Then came the evacuation. As fire roared on the right side from fuel lines cut by the flying metal, 170 passengers and crew made it out alive, 21 of them suffered slight injuries.
The NTSB has identified at least three previous similar engine failures the past 16 years. But unless investigators determine a connection or some systemic problem in these engines, it is unlikely there would be an emergency order from the FAA.
Federal inspectors are still going over the American plane's maintenance records.
PASSENGERS DESCRIBE THEIR EXPERIENCE ON THE PLANE
WATCH: Gary Schiavone describes his experience on AA383
Passenger Hector Cardenas said the plane was seconds away from taking off when he heard an explosion. Large flames and a plume of black smoke could be seen rising from the aircraft.
WATCH: Hector Cardenas describes his experience on the plane
"Within 10 or 15 seconds we would have been in the air," Cardenas said.
Sarah Ahmed was also on the flight and described the chaos in the moments after the fire broke out.
"We were almost up in the air. We were full throttle, full speed ahead and then we heard this huge bang and there's fire at the window, and so everyone on the right side of the plane got up, jumped up and they'er now on the left side of the plane. So there's a stampede at the left side. The plane comes to a screeching stop. People are yelling 'open the door, open the door!' everyone's screaming and jumping on top of each other to open the door. Within that time, I think it was seven seconds, there was now smoke in the plane and the fire is right up against the windows and it's melting the windows," Ahmed said.
WATCH: Sarah Ahmed describes her experience no the plane
Conversation between the cockpit and air traffic control revealed how quickly the situation unfolded.
Pilot: "American 383 heavy stopping on the runway."
Tower: "Roger, roger. Fire."
Pilot: "Do you see any smoke or fire?"
Tower: "Yeah fire off the right wing."
Pilot: "Ok, send out the truck."
Tower: "Sending them."
Tower: "American 383 can you give us any information right now?"
Pilot: "Uh, standby. Chicago American 383, we're evacuating."
Tower: "American 383 roger, trucks are on the way."