India’s aviation regulator mandated on Monday that airlines operating various Boeing models inspect fuel control switches. This action comes days after an investigation into the Air India plane crash last month revealed these switches were turned off, cutting off fuel supply to both engines.

India’s Directorate General of Civil Aviation indicated that the directive pertained to Boeing 787 Dreamliners and certain Boeing 737 variants, requiring airlines to complete inspections and report their findings by July 21.

A preliminary report into the Air India crash, which resulted in 260 fatalities in Ahmedabad, found that the switches were flipped within one second of each other, halting fuel to both engines. Released last week, the report did not provide conclusions about the crash’s cause, nor did it explain how the switches shifted from the run position to the cutoff in-flight.

The movement of the fuel control switches allows and cuts fuel flow to the plane’s engines.

The Boeing 787-8 Dreamliner crashed on June 12 shortly after takeoff. It killed all but one of the 242 people on board as well as 19 people on the ground.

According to the report, cockpit voice recordings captured a moment of confusion between the pilots, with one asking the other why he cut off the fuel. “The other pilot responded that he did not do so,” the report said.

Some aviation experts in India speculated the crash was caused due to human error based on the preliminary report. At least two commercial pilots’ associations have rejected such claims.

The Indian Commercial Pilots’ Association in a statement on Sunday said it was “deeply disturbed by speculative narratives … particularly the reckless and unfounded insinuation of pilot suicide.”

Air India CEO Campbell Wilson on Monday said the preliminary report into the crash of the London-bound plane found no mechanical or maintenance issues with the aircraft and its engines.

In an internal memo to airline staff seen by The Associated Press, Wilson said the report stated that all mandatory maintenance tasks of the aircraft had been completed.

“There was no issue with the quality of fuel and no abnormality with the take-off roll. The pilots had passed their mandatory pre-flight breathalyser and there were no observations pertaining to their medical status,” he said in the note.

After the crash, Indian authorities ordered deeper checks of Air India’s entire Boeing 787 Dreamliner fleet to prevent future incidents. Air India has 33 Dreamliners in its fleet.