At least 130 people have been rescued and one body recovered after a boat sank en route to Australia.
An air and sea search was still ongoing for those missing, the Australian Maritime Safety Authority (AMSA) said.
Prime Minister Julia Gillard said that there were 133 people on board the vessel and that two Australian warships and an air force aircraft that can drop life rafts had joined the search on Wednesday.
The wooden Indonesian fishing boat, believed to be carrying asylum seekers, including women and children, capsized en route to Australia's Christmas Island, the AMSA said.
Authorities were alerted at approximately 6:17am local time on Wednesday (20:17 GMT on Tuesday), the AMSA said.
A merchant vessel arrived at the scene about four hours later, advising the AMSA that the stricken vessel had sunk, and that survivors were in the water. A second merchant vessel later joined the rescue.
The accident comes less than a week after another boat, with around 200 people on board, sank in the Indian Ocean, also on its way to Australia.
Rescuers managed to save 110 people and 17 bodies were recovered, but no other survivors have been found.
Rickety, often overloaded vessels packed with desperate migrants regularly make for the Australian coast, setting out mainly from Indonesia. Some vessels also originate from Sri Lanka.
Hannah Harborow, a coordinator with Amnesty International in Australia, said there is an increase in asylum seekers around the world and turning them away is not the solution.
“What we have to address is why people are getting on the boats,” Harborow told Al Jazeera. “And this includes coming up with a regional framework working with countries like Malaysia and Indonesia in improving their protection systems in those countries to stop people from getting on the boats.”
Though they come in relatively small numbers by global standards, two per cent according to Harborow, asylum-seekers are a sensitive political issue in Australia, dominating 2010 elections due to a record 6,555 arrivals.
Australian political parties remain deadlocked on how to deal with the influx of migrants. Both sides of the political spectrum support offshore processing of asylum-seekers, but differ on where it should occur.
Last year, the government sealed a deal to send 800 boat-people to Malaysia in exchange for 4,000 of that country's registered refugees, in a bid to deter people-smugglers from undertaking the dangerous maritime voyage to the continent.
Gillard's fragile coalition government was unable to pass the required legislation through parliament without opposition support, however. The deal was also marred by concerned that Malaysia was not a signatory to the UN refugee conventions.
"It’s not illegal to seek asylum whether you come by boat or by plane in Australia and the solution is not to push the boats back," Harborow said.