WASHINGTON (AP) — A U.S. government agency said Tuesday that China has granted visas for federal investigators to travel there and aid in the investigation of the deadly China Eastern Airlines crash.

The National Transportation Safety Board said China also granted visas to technical advisers from Boeing, which made the plane, engine manufacturer CFM and the Federal Aviation Administration. All would take part in the investigation, under longstanding international agreements.

The safety board said the U.S. officials and industry representatives hope to leave for China this week.

A safety board spokesman said the independent agency will send a “small group” including senior air-safety investigator Sathya Silva to China.

Their travel was held up for several days to meet Chinese visa and COVID-19 regulations, and the NTSB appealed to the State Department to intervene.

A China Eastern Boeing 737-800 jet crashed in a remote mountainous area in southern China on March 21, killing all 123 passengers and nine crew members on board. The plane was cruising at about 29,000 feet (8,800 meters) about one hour into its flight from Kunming in southeastern China to Guangzhou, an export manufacturing hub near Hong Kong, when it went into a steep descent.

Over the weekend, searchers found the plane’s flight data recorder, following earlier recovery of the cockpit voice recorder, which investigators hope will provide important clues about the cause of the crash.

China Eastern, one of four major Chinese airlines, and its subsidiaries have grounded all their Boeing 737-800s, more than 200 planes. The airline said the grounding was a precaution, not a sign of any problem with the planes.

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