India would not allow a UN investigator to join a probe of a crashed Air India jet that some safety experts had criticized for delays in analysis of crucial black box data, two senior sources familiar with the matter told Reuters.

Indian investigators said Thursday that they began analyzing data from black boxes recovered from the fatal Air India crash — information that is expected to help answer why the London-bound Boeing 787-8 jetliner carrying 242 passengers and crew members crashed shortly after takeoff from Ahmedabad Sardar Vallabhbhai Patel International Airport earlier this month.

Investigators have started analyzing data from the black boxes of the Air India Boeing 787 that crashed two weeks ago, killing at least 270 people