The investigation into the Air India plane crash that killed more than 240 people is focusing on the engine, flaps and landing gear, a source said on Friday, as the aviation regulator ordered safety checks on the airline's entire Boeing-787 fleet.

The Boeing 787-8 Dreamliner with 242 people on board bound for Gatwick Airport south of London began losing height moments after take-off over a residential area of the western city of Ahmedabad and erupted in a huge fireball as it hit buildings below, CCTV footage showed.

Only one passenger survived, and local media reported that as many as 24 people on the ground were also killed as the plane crashed onto a medical college hostel during the lunch hour. Reuters could not immediately verify the number.

It was the world's worst aviation disaster in a decade.

On Friday, a source with direct knowledge of the matter told Reuters that Air India and the Indian government were looking at several aspects of the crash including issues linked to its engine thrust, flaps and why the landing gear remained open as the plane took off and then came down within moments.

The probe is also looking at whether Air India was at fault, including on maintenance issues, the source said.

A possible bird-hit is not among the key areas of focus, the source said, adding that teams of anti-terrorism experts were part of the investigation process.

The government is considering whether it should ground the Boeing-787 fleet in the country during the probe, the source said. There was no immediate response to requests for comment on that from Air India, Boeing and the aviation ministry.

Air India has more than 30 Dreamliners that include the Boeing 787-8 and 787-9 versions. A source in Air India said there had been no communication so far from the government on the possible grounding.

Separately, India's aviation regulator ordered Air India to conduct additional maintenance actions on its Boeing 787-8/9 aircraft equipped with GEnx engines, including "one-time check" of the take-off parameters before the departure of every flight from midnight of June 15.

The airline has also been instructed to introduce "flight control inspection" – checks to ensure control systems are working properly – in transit inspection, and to conduct power assurance checks, meant to verify the engine's ability to produce the required power, within two weeks.

The aviation ministry said that investigators and rescue workers had recovered the digital flight data recorder – one of the two black boxes on the plane – from the rooftop of the building on which the jet crashed.

There was no information on the cockpit voice recorder, the other black box, which is also crucial to the crash probe.