Rear Admiral Michael LeFever said a military investigation into the November 1 incident was inconclusive but he said he was satisfied the CH-47 Chinook never came under fire.

"We didn't think it was that kind of event when we reviewed the facts, and so we're continuing to fly everywhere," he told reporters here via video link from Islamabad.

Lefever said a review of the incident established that, as Pakistani authorities had said, boulders were being blown up at the time to clear roads in the Chakothi area.

"The evidence was probably a little bit inconclusive. There was explosions going on. We had an observer that thought he saw something. And at the end of the day there wasn't anything definite there that we could hold our hat on," he said.

Lefever said US helicopters have since flown into Chakothi several times without incident to deliver relief supplies.

LeFever said about 975 US military personnel are now taking part in the relief operations, and the number is expected to grow to about 1,200 in the coming days as winter descends on the mountainous area.

Two dozen US military helicopters have been ferrying supplies and moving people around the area affected by the earthquake, which is estimated to have killed some 75,000 people, and left millions homeless.

A US Army surgical hospital from Europe is operating in Muzaffarabad, Pakistan and a marine corps surgical unit based in Japan will be deployed as early as next week in the Shinkiari region in the Northwest Frontier province, he said.

US Navy engineers based in Muzaffarabd also are working on construction projects identified by the Pakistanis, he said.

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