A U.S. Navy oceanographic survey ship was trying to determine Wednesday if large pieces of round metal found off Sulawesi Island's western coast were the wreckage of a Boeing 737 that disappeared more than a week ago carrying 102 people.

Thousands of soldiers, police and volunteers, meanwhile, continued their search on land and were headed to two points located by U.S. National Transportation Safety Board.

An Indonesian vessel earlier reported three pieces of debris on the seabed after local fisherman told authorities they had spotted a low-flying, unstable aircraft in the area but lost sight of it after hearing a loud bang, naval officials said.

The USNS Mary Sears, which has sonar and satellite imagery capabilities, was called in to see if the metal could be the remnants of Adam Air Flight KI-574, said Eddy Suyanto, the search and rescue mission chief.

The debris was found in several locations on the Makassar Strait seabed, roughly 2 1/2 miles from the West Sulawesi provincial capital of Mamuju and at a depth of around 1,500 yards, he said.

Rear Admiral Moekhlas Sidik, commander of Eastern Indonesia Fleet, said the Mary Sears had confirmed one of the objects was "round-shaped metal," but that more readings were needed to identify it.

The pilot of the Adam Air plane, which left Java island for the North Sulawesi provincial capital of Manado on Jan. 1, twice changed course after battling 80 mph winds but did not issue a mayday or report technical difficulties, officials said.

With no emergency location signal to guide more than 3,600 soldiers, police and volunteers searching in the island's dense jungles and surrounding seas, teams have fanned out over a nearly 30,000-square-mile area.

On Wednesday, they combed two areas recommended by U.S. National Transportation Safety Board after it analyzed historical radar data from the day of the disappearance, Suyanto said.

After mistakenly claiming last week that the wreckage had been found with 12 survivors, officials were cautious Tuesday in discussing the discovery of the underwater debris.

Indonesia said it welcomed all international assistance in the search.

A Canadian Defense Ministry airplane with inland mapping capabilities, which had been working in the tsunami-ravaged province of Aceh, joined the search Tuesday, Suyanto said, and Singapore also has been providing aerial surveys.

A U.S. National Transportation Safety Board team arrived late last week and authorities in the United States were viewing satellite imagery of the island, the embassy said.

Adam Air is one of about 30 budget carriers that sprang up in Indonesia after the industry was deregulated in 1998. The rapid expansion has led to cheap flights throughout Indonesia, but has raised concerns about maintenance.

Three Americans — a man from Oregon and his two daughters — were among the plane's 96 passengers. It was not clear if any other foreigners were on board.