SYDNEY -- Planes and ships searching a remote patch of the Indian Ocean found no signs Tuesday of additional survivors from the sinking of a suspected asylum-seeker boat. Eleven people were believed missing, while 27 were rescued.

Merchant ships that responded to distress calls from the stricken vessel plucked dozens from the sea on Monday, a day after it went down. Some of the survivors swam to a life raft dropped by an Australian military plane, officials said. One person taken aboard a rescue vessel died.

Australian Home Affairs Minister Brendan O'Connor said a Japanese fishing vessel would join the search Tuesday. The merchant ship LNG Pioneer remained in the area and seven Australian aircraft were also searching the waters. A Taiwanese fishing trawler that had helped rescue survivors was leaving to refuel, he said.

"We'll do everything we can...to recover people that are in the water but of course there are grave concerns for the safety of these 11 people," O'Connor said.

The nationalities of the people on the sunken boat were not known and Australian officials have refused to speculate on whether they were asylum seekers trying to reach Australia. But aspects of the emergency “such as an unseaworthy boat carrying so many people in waters sometimes used by human traffickers” signaled that may be the case.

The origins of the boat and the reason for its journey would be investigated after the search and rescue phase is over, O'Connor said.

The boat went down late Sunday about 400 miles (650 kilometers) from the Cocos Islands, sparsely populated atolls about 1,500 miles (2,400 kilometers) northwest of the Australian coast and about 800 miles (1,300 kilometers) south of Indonesia.

An air force cargo plane reached the area Monday afternoon after hours of flying, and spotted two survivors in the water, O'Connor said. It dropped a life raft to them and continued to scour the search zone. Prime Minister Kevin Rudd said later that three other people who were clinging to timber were also seen paddling toward the raft.

The boat went down in international waters, but with Australia's area of responsibility for search and rescue operations.

There has been a surge of boats carrying asylum seekers toward Australia. Some 35 boats carrying about 1,770 asylum seekers have arrived in Australian waters this year, mostly from Iraq, Afghanistan, Iran, and Sri Lanka.

Many of them pay thousands of dollars to people smugglers who send them to sea in leaky boats from Indonesia and sail south. Most are caught by customs authorities and are detained in an immigration camp on remote Christmas Island while their refugee applications are assessed, a process that can take months or years. (AP)