MAKASSAR, Indonesia (Reuters) - An Indonesian navy ship searching for a missing commercial airliner detected a large undersea object off the west coast of Sulawesi on Monday, but it has not been confirmed whether it was the plane.
The 17-year-old Boeing 737-400 operated by Indonesian budget carrier Adam Air went missing in bad weather a week ago after its pilot reported crosswinds and asked for safe coordinates from the airport in Makassar, Sulawesi island's largest city.
"We suspect that it was a metal object 1,050 metres (1,148 yards) under the sea off Mamuju. It could not be confirmed yet whether it was the Adam Air plane," Tony Syaiful, the spokesman of the navy's Eastern Fleet, told Jakarta-based Radio Elshinta.
Mamuju is a seaside town in West Sulawesi province.
The USNS Mary Sears, a U.S. ship with sonar capability and the ability to detect metal underwater, will arrive on Tuesday to join the search, which already includes at least four ships, two Indonesian air force planes, two helicopters, and thousands of troops and police on the ground.
Separately, a military spokesman said on Monday two more Indonesian Air Force helicopters will take part in the search.
The search was focused on the Bone Strait between the two southern arms of Sulawesi island and the onshore areas of western Sulawesi, Captain Mulyadi said in Makassar, from where efforts are being coordinated.
Indonesian officials will be cautious in announcing any discovery after erroneously saying the plane had been spotted in Sulawesi's mountains on Tuesday when accounts from a local village were relayed to the highest level without checks.
The ill-fated plane heading for North Sulawesi provincial capital Manado carried 96 passengers and six crew.
The search has been hampered by bad weather, with the area's jungle-covered mountains also making it difficult to spot things from the air.
The region lacks roads and communications are often poor.
In addition to the U.S. ship and an American military plane, foreign aid has included a Singapore Air Force Fokker-50 search plane.
"The United States has extended their help. The foreign ministry will not hesitate in giving permission and clearance for their efforts in helping us," Indonesian Foreign Minister Hassan Wirajuda told reporters in Jakarta on Monday.
The pilot made no distress call from the plane, which took off from Surabaya on Java island on Jan. 1 for Manado, provincial capital of North Sulawesi.
The plane disappeared less than three days after a ferry with more than 600 aboard capsized and sank off Java.
Fourteen survivors of the ferry have been rescued after drifting on a life raft for nine days, a top search and rescue official said on Monday.
At least 248 survivors have been found, some clinging to wreckage or floating in life vests, and others on life rafts.
The latest survivors were found about 480 km from the accident site early on Sunday morning, according to Karnoyudho, who is head of the national search and rescue agency.
Indonesian President Susilo Bambang Yudhoyono has called for an investigation into what went wrong in both cases as well as a general probe into the state of Indonesia's transport system.
The network serves 220 million people in an archipelago of 17,000 islands.
(With additional reporting by Muara Makarim, Achmad Sukarsono and Muhammad Azhari in Jakarta)