NEW DELHI, India: India has decided not to allow a United Nations (UN) investigator to join the investigation into the recent Air India plane crash, according to two senior sources who spoke to Reuters.

Some safety experts had already raised concerns about delays in examining the plane's black box data.

Earlier this week, the UN's aviation agency offered to send one of its investigators to help with the case. The crash, involving a Boeing 787-8 Dreamliner, happened in Ahmedabad on June 12 and killed 260 people. It was the deadliest aviation accident in the world in the last ten years.

In the past, the UN agency—called the International Civil Aviation Organization (ICAO)—has only sent investigators when countries asked for help. For example, it helped with the investigation into a Malaysian plane in 2014 and a Ukrainian plane in 2020. This time, however, ICAO offered help on its own and asked that its investigator in India be allowed to observe the investigation. But Indian officials turned down the offer, the sources said. This was first reported by the news channel Times Now on June 26.

India's Aircraft Accident Investigation Bureau (AAIB), which is leading the investigation, did not respond to questions, and ICAO also did not comment.

India's civil aviation ministry said this week that it had retrieved and begun work on the flight recorder data about two weeks after the crash. However, experts had earlier questioned why there was so little information available, especially about the black box that was found on June 13 and another part that was recovered on June 16.

Doubts exist about where the black box data would be read—India or the United States—since the U.S. National Transportation Safety Board (NTSB) is also involved.

So far, the Indian government has only held one press conference and did not take questions from reporters.

According to international aviation rules (known as "Annex 13"), decisions about where to read flight recorder data should be made quickly to help prevent future accidents.

An unnamed Indian aviation ministry official said earlier this week that the government is following all ICAO rules and that the media has been informed of major updates.

Most plane crashes are caused by a mix of problems, and the first report is usually expected about 30 days after the crash.