The engine of a British Airways plane which burst into flames during take-off was found to have "multiple breaches" in its casing, investigators have said.
In an initial report into the fire, the National Transportation Safety Board (NTSB) said parts of the engine's high pressure compressor component had been found on the runway.
The London-bound Boeing 777-200 caught fire as it was taking off at a Las Vegas airport on Wednesday, forcing 157 passengers, 10 crew and three pilots to evacuate down emergency slides.
The plane's left GE90-85B engine, its fuselage and wing were "substantially damaged" by the fire, according to the NTSB.
In a statement, investigators said: "Initial examination of the left engine revealed multiple breaches of the engine case in the area around the high pressure compressor.
"Examination of the material recovered from runway found several pieces of the high pressure compressor spool (approximately 7-8in in length)."
The cockpit voice and flight data recorders have been sent away for analysis.
The NTSB added: "The powerplants and airworthiness groups will continue documenting the airplane and engine over the next several days. It is anticipated that once the tooling is in place, the left engine will be removed and shipped to a facility to conduct a full teardown."
Dr Colin Brown, from the Institution of Mechanical Engineers, told the BBC the engine casing was designed to contain any damage, and it was "most likely" the high pressure compressor spool suffered from a "fatigue crack".
If this was the case, he added, aircraft with similar engines could be grounded to check for issues.
CNN reported that a source close to the investigation noted the plane's fire suppression equipment was deployed but failed to extinguish the blaze.
Investigators are considering whether the equipment worked properly, or whether the fire spread due to a ruptured fuel line, the report added.
BA issued a statement which said the plane ''experienced a technical issue''.
The aircraft was travelling between 40 and 100mph ahead of the 10-hour flight to Gatwick when the captain slammed the brakes on.
Twenty-seven people, including all crew members, were taken to hospital with minor injuries, mostly caused by sliding down the inflatable chutes to escape.
The captain, Chris Henkey, 63, from Reading, Berkshire, has 42 years of flying experience with BA and was on his penultimate flight before leaving the profession.
But he told NBC News he is "unlikely" to make his final flight, which would have taken him to Barbados to join his daughter in his favourite holiday destination.
"It's safe to say I'm finished flying," Mr Henkey said.
BA would not reveal how many of the passengers were British, although the Las Vegas to Gatwick route is popular with UK leisure travellers.