Investigators probing the catastrophic Air India crash in Ahmedabad are reportedly narrowing their focus on alleged pilot action in the final moments before the aircraft plunged from the sky in a deadly fireball, killing 260 people.

Sources close to the investigation say the inquiry is increasingly leaning towards the possibility that actions taken in the cockpit played a decisive role in the disaster, which unfolded shortly after take-off on June 12 last year. Mechanical failure has been ruled out by experts, and there is still no evidence to suggest sabotage, according to reporting by Bloomberg, leaving pilot input as the strongest remaining line of inquiry.

The claims, described by sources as highly sensitive and not yet made public, have intensified months of speculation surrounding the crash. An initial investigative report found that fuel control switches on the Boeing 787 Dreamliner were moved to the “cut-off” position moments after lift-off, depriving the aircraft of power at a critical stage of flight.

At the controls was Sumeet Sabharwal, a 56-year-old veteran captain with more than 15,000 flying hours, over 8,000 of them on the Dreamliner. The aircraft, carrying 230 passengers and 12 crew on a flight to London Gatwick, failed to climb and slammed into a medical students’ hostel near Ahmedabad, killing everyone onboard except one passenger.

The narrative surrounding the tragedy has shifted repeatedly.

While early findings raised serious questions about cockpit actions, an Indian court later came to the pilots’ defence, stating that “nobody can blame him for anything”, prompting renewed debate over responsibility.

A final report into the causes of the crash is due to be published in June, one year on from the disaster, although investigators are expected to release their conclusions earlier, The Sun reported.

One of the final stages of the inquiry was completed in December, when officials from India’s Aircraft Accidents Investigation Bureau travelled to the United States to analyse cockpit voice recordings and flight data.

That analysis focused on determining whether the fuel control switches were intentionally moved. Investigators used specialist technology to isolate the distinctive sound made when the switches are activated, though sources said the task was complicated by heavy background noise during take-off.

The allegations against Captain Sabharwal were first reported by the Wall Street Journal, citing US officials who claimed black box recordings captured a tense exchange in the cockpit shortly before the crash.

Sources familiar with the American investigation allege it was Sabharwal who reached for the switches after the aircraft lifted off the runway, sealing the plane’s fate.

His family has strongly disputed those claims. Pushkaraj Sabharwal, the captain’s 91-year-old father, told investigators his son was a highly skilled and disciplined pilot who regularly passed aviation exams.

He accused US officials of bias and called for an independent investigation to explore alternative explanations.

Harrowing CCTV footage shows the Dreamliner accelerating down the runway at Sardar Vallabhbhai Patel International Airport at around 1.38pm local time before lifting off, appearing to lose power almost immediately and then plunging back to the ground.

Among the dead were 53 British nationals. One British man survived after jumping from the burning wreckage and was filmed walking away from the crash site in scenes described as miraculous.

Captain Sabharwal, who was reportedly just months from retirement, had recently been grieving the death of his mother while caring for his elderly father. Long regarded as steady and reliable, he now sits at the centre of one of the most controversial aviation investigations in recent history.

The final report is expected to draw a line under months of speculation and provide definitive answers about what caused one of India’s deadliest air disasters.