BEIJING/SHANGHAI (Reuters) - China’s aviation regulator on Monday grounded nearly 100 Boeing Co 737 MAX 8 aircraft operated by its airlines, more than a quarter of the global fleet of the jets, after a deadly crash of one of the planes in Ethiopia.

However, a U.S. official said it was unclear what information the Chinese regulator was acting on because the investigation of Sunday’s crash, the second involving the latest version of the narrowbody jet, was in the early stages.

Speaking on condition of anonymity as the topic is sensitive, the U.S. official said there were no plans to follow suit, as the jet had a stellar safety record in the United States and there was a lack of information on what caused the Ethiopian crash.

Boeing, whose shares dropped 9 percent in U.S. pre-market trade, said the investigation remained in its early stages and it had no basis to issue new guidance to operators.

It was unusual to ground a plane type unless a specific mechanical issue or component failure had been identified and could be inspected, said Andrew Herdman, director general of the Association of Asia Pacific Airlines.

“In this case it is not clear what the action item is, having done the suspension,” he said. “What is lacking now is what happened in this case.

“That means finding the black boxes and piecing together other circumstantial evidence from air traffic control recordings and so on.”

Most other Boeing 737 MAX operators globally told Reuters their planes would keep flying and they had no plans to cancel orders.

Sunday’s crash, minutes after take-off, of an Ethiopian Airlines 737 MAX 8 bound for Nairobi, killed all 157 on board and prompted the carrier to ground the rest of its 737 MAX jets.

In October, a 737 MAX 8 operated by Indonesian budget carrier Lion Air crashed 13 minutes after take-off from the Indonesian capital of Jakarta on a domestic flight, killing all 189 on board. The 737 MAX 8 first entered service in 2017.(FA)