(CNN) -- Engine covers that flew off and damaged a British Airways plane upon takeoff last week had been left unlatched during maintenance, British aviation investigators said in a preliminary report Friday.
The damage prompted the pilots of British Airways Flight 762 to make a safe emergency landing at London's Heathrow Airport shortly after takeoff there May 24.
An investigation of the flight determined that the covers, called fan cowl doors, were "left unattached during maintenance and this was not identified prior to aircraft departure" from Heathrow, said Friday's bulletin from the Air Accidents Investigation Branch.
The flyaway doors punctured the right engine's fuel pipe and damaged other systems, leading to a loss of thrust control and eventually an engine fire, said the report from AAIB, part of the UK Department of Transport.
The flight, initially bound for Norway's capital and carrying 75 passengers and five crew members, made an emergency landing less than 30 minutes after takeoff. Firefighters extinguished a small fire at the right engine.
Passengers were evacuated from the plane on emergency slides after landing, and three people were treated for minor injuries, officials said.
The left engine performed normally throughout the flight, the bulletin said.
British Airways chief executive Keith Williams said the airline is "precluded from releasing or discussing any additional details while the AAIB investigation is ongoing."
"We welcome the publication of the AAIB interim report," he said. "We continue to cooperate fully with the investigation team and can confirm that appropriate initial action has already been taken in accordance" with the bulletin.
CNN's Per Nyberg contributed to this report.