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.

Search crews sifting through the wreckage of the Air India jetliner that crashed last week retrieved the second black box, as they seek to gain more evidence to understand what caused the accident that killed all but one of the 242 people on board.

Tragedy struck this week when a plane crashed in the city of Ahmedabad just shortly after takeoff, leaving investigators and aviation officials with many questions.