“Mayday, mayday,” was the final radio message sent by the pilot of the Air India 171 flight bound for London, moments before it crashed to the ground, killing more than 270 people.

In a briefing by India’s aviation authorities on Saturday, authorities confirmed that Captain Sumeet Sabharwal, who was piloting the flight, sent a distress call to air traffic control less a minute after it took off from Ahmedabad airport at 1:39pm on Thursday.

When air traffic control responded to the pilot’s emergency mayday call, “there was no response”, said Samir Kumar Sinha, a secretary for India’s aviation ministry. He said the plane went down seconds later.

Sinha said that initial investigations had shown the plane had reached a height of 650ft after takeoff, after which it began to rapidly descend and hit the ground in Meghani Nagar, 2km from Ahmedabad airport.

The 227-tonne plane crashed into a hostel where medical students and their families were living. All but one of the 242 people on board were killed in one of India’s worst aviation disasters in decades.

The collision with the hostel also killed at least three student doctors and one doctor’s wife who was heavily pregnant, as well as several labourers and vendors working in the area.

Indian aviation authorities would not be drawn into conjecture on the cause of the crash of the Boeing 787-8 Dreamliner, which has been the source of global speculation, but emphasised that “every theory going around about the crash will be looked at”.

Sinha said the flight data recorder, known as the black box, had been recovered and was being looked into by investigators. A complete assessment of the incident would be completed within three months.

Ram Mohan Naidu Kinjarapu, the civil aviation minister, told the press briefing: “The decoding of this black box is going to give in-depth insight into what would have actually happened during the process of the crash.”

A team of four UK aviation accident experts arrived in Ahmedabad, in the west Indian state of Gujarat, on Friday night to assist in the crash investigation.

By Saturday morning, the death toll had risen to at least 274, as investigators continued to comb through the wreckage and another body was recovered from beneath the wing of the plane. Families of the victims continued to gather at the Civil hospital in Ahmedabad where the dead were brought, as anger and frustration grew at the delay in handing over the bodies of their loved ones.

Anil Patel, who lost his son Harshit, 30, and daughter-in-law Pooja, 28, in the crash, was increasingly agitated at the delay. He was among hundreds of relatives who had submitted DNA samples to help identify his son’s body but said he had received no information since.

“We still don’t know exactly when we’ll get the body,” he said. He described his son and daughter-in-law as “all I had left” after his wife died of cancer six years ago. Harshit had moved to London two years ago but would video call his father every day.

“Even yesterday, when I was sitting outside the postmortem block, I could smell the stench of charred bodies from inside,” said Patel. “It’s hard to accept that my son is also lying in there. I just want to bring them home soon. The longer they stay there, the more they’ll deteriorate. I just can’t bear the thought.”

Authorities emphasised that the task of identifying people, whose bodies may have been heavily charred or dismembered from the force of the crash, was a complex task, slowing down the process of returning the victims to their families.

“We are dealing with at least 250 samples, and for each match, we have to cross-verify it against this entire pool. It’s a process of elimination, and that naturally takes time,” said one official, speaking at the hospital, emphasising that the team at the hospital had been working through the night to accurately match the DNA to the bodies.

The sole surviving passenger, Vishwash Kumar Ramesh, whose escape from death was widely described as a “miracle” by experts, remained in hospital in Ahmedabad under observation but was said to be recovering.

Dr Gameti, of Ahmedabad Civil hospital, said Ramesh was “doing very well and will be ready to be discharged any time soon”.