Updated

Air accident investigators say a British Airways jet that made an emergency landing at Heathrow Airport last week lost panels from both its engines after they were left unlatched during maintenance.

In an initial report on the incident Friday, the Air Accidents Investigation Branch said the unlatched fan cowl doors weren't noticed before the Airbus A319-131 took off.

The covers detached, damaging the airframe and some aircraft systems and rupturing a fuel pipe on the plane's right engine, which developed an external fire.

Britain's busiest airport was briefly closed May 24 after the Oslo-bound flight made an emergency landing shortly after takeoff.

TV footage showed smoke streaming from one of the engines. The 80 passengers and crew were evacuated without serious injuries, and fire crews quickly put out the blaze.