The Air Accidents Investigation Branch (AAIB) said an initial report on the crash would be available within 48 hours.
No engine power
Reports in the UK's Financial Times and by the British Press Association have said that the aircraft lost power as it came in to land, possibly affecting both engines.
BA and AAIB officials refused to speculate on possible causes immediately.
All passengers and crew will be questioned and the "black box" flight data and cockpit voice recorder checked.
David King, the air accidents chief inspector, said it could take over a month for the final investigation report to be published.
Robin Tydeman, a former RAF and commercial pilot and an air accident investigator for 10 years, has been put in charge of investigation.
The flight from Beijing departed at 9.42am (0142 GMT) local time and was forced to land 18 minutes earlier than its 1pm landing time in London.
Witnesses said the aircraft was flying at a low level – as if "you could lean out the window and touch it", one onlooker said - and banking heavily.
The airplane was fully evacuated on landing.
A spokesman for the police said that there was no suggestion that terrorism was involved.
The accident occurred just before a jet carrying Gordon Brown, the British prime minister, and a delegation of business leaders, including Richard Branson, the Virgin chairman, was about to depart for China.
Brown's aircraft was about a half mile away.