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.

Investigators have begun analyzing data from the black boxes recovered from the Air India Boeing 787 jet that crashed earlier this month, killing 270 people.

The new and advanced AAIB lab, built by support of government-owned Hindustan Aeronautics Ltd (HAL) and inaugurated in April, has enhanced the agency’s ability to repair damaged black boxes, retrieve data,