Investigators in India are studying the black boxes of a Boeing 787 Dreamliner after recovering them from the aircraft wreckage to ascertain the cause of last week’s plane crash that left at least 270 people dead.

Officials say at least 270 bodies have been recovered, while the lone surviving passenger is still under observation for some of his injuries.

An Air India flight from Delhi to Zurich was delayed on Sunday due to mandatory checks on Boeing 787-8 aircraft, resulting in its late arrival in Switzerland close to the night curfew, sources said on Monday.

Authorities have started handing over remains of the victims of one of India’s worst aviation disasters after identifying some through DNA tests, days after the Air India flight crashed and killed at least 270 people in Gujarat state,