By Sudipto Ganguly, Abhijith Ganapavaram and Aditya Kalra

AHMEDABAD, India (Reuters) -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-terror 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.

ONE BLACK BOX FOUND

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.

Earlier on Friday, rescue workers had finished combing the crash site and were searching for missing people and bodies in the buildings as well as for aircraft parts that could help explain why the plane crashed soon after taking off.

Indian Prime Minister Narendra Modi was briefed by officials on the progress of rescue operations when he visited the crash site in his home state of Gujarat on Friday. Modi also met some of the injured being treated in hospital.

"The scene of devastation is saddening," he said in a post on X.

Thursday's crash was the first for the Dreamliner since the wide-body jet began flying commercially in 2011, according to the Aviation Safety Network database.

The plane that crashed on Thursday flew for the first time in 2013 and was delivered to Air India in January 2014, Flightradar24 said.

The passengers included 169 Indian nationals, 53 Britons, seven Portuguese and one Canadian.

Indian conglomerate Tata Group took control of the formerly state-owned Air India in 2022, and merged it with Vistara - a joint venture between the group and Singapore Airlines – last year.

(Reporting by Sudipto Ganguly, Abhijith Ganapavaram, Sumit Khanna and Mahezabin Saiyed in Ahmedabad, Aditya Kalra and Shivam Patel in New Delhi; additional reporting by Hritam Mukherjee in Bengaluru; writing by Tanvi Mehta and YP Rajesh; Editing by Saad Sayeed, Kate Mayberry, Philippa Fletcher)