By Aditya Kalra, Allison Lampert and David Shepardson

June 25 (Reuters) - 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.

Earlier this week, the United Nations aviation agency took

the unusual step of offering India one of its investigators to

provide assistance following the Boeing 787-8 Dreamliner

crash killing 260 people in Ahmedabad on June 12.

Previously, the International Civil Aviation Organization

has deployed investigators to help with certain probes, such as

the downing of a Malaysian plane in 2014 and a Ukrainian

jetliner in 2020, but those times the agency had been asked for

assistance.

ICAO had asked for the investigator who was in India to be

given observer status, but Indian authorities refused the offer,

the sources said. The news was first reported on Thursday by the

Indian news channel Times Now.

India's Aircraft Accident Investigation Bureau (AAIB), which

is leading the probe into the world's deadliest aviation

accident in a decade, did not return a request for comment. ICAO

was not immediately available for comment.

India's civil aviation ministry said on Thursday that

investigators downloaded flight recorder data around two weeks

after the crash.

Previously, safety experts had questioned a lack of

information about the probe, including the status of the

combined black box unit recovered on June 13, along with a

second set that was found on June 16.

Questions were also raised on whether the recorders would be

read in India or in the U.S. since the National Transportation

Safety Board is participating in the investigation. The Indian

government held only one press conference on the incident, and

no questions were taken.

Under international rules known throughout the industry by

their legal name "Annex 13," the decision of where to read

flight recorders should be made immediately in case the evidence

obtained could avert future tragedies.

Earlier this week, an Indian aviation ministry official who

declined to be named said the department has been "following all

the ICAO protocols." The official added that media

representatives have made updates on important events.

Most air crashes are caused by multiple factors, with a

preliminary report expected about 30 days after the accident.

(Aditya Kalra in New Delhi, Allison Lampert in Montreal and

David Shepardson in Washington; Editing by David Gregorio)