At least four people are dead after an asylum seeker boat capsized 70 nautical miles north of Christmas Island on Tuesday.
Australian Border Protection and Customs says 144 people were rescued from the water by two Navy ships, the HMAS Warramunga and HMAS Albany.
In a statement, Customs says the ships had been escorting the boat to Christmas Island after it ran into trouble, but it capsized on the way.
A Royal Australian Air Force P3-Orion maritime patrol aircraft deployed a number of life rafts.
"It is believed that there were approximately 150 people on board based on an assessment of information provided by the vessel's crew," the Customs statement said.
"This number has been revised downwards from an initial estimate of up to 180 people."
A search was suspended shortly after 9:30pm (AEST).
On the weekend, a baby boy died at sea after an asylum seeker boat carrying nearly 100 people sank near Christmas Island.
A search for eight missing people was suspended on Sunday, with the Australian Maritime Search and Rescue Authority (AMSA) saying the decision was based on the high probability that it was unlikely there would be any more survivors found.
Confirmation of the latest fatalities at sea came just hours after Prime Minister Kevin Rudd spoke about some of the challenges posed by people smuggling.
The Federal Government is reviewing Australia's system for processing asylum seekers and Mr Rudd is expected to announce a revamped policy in the next few days.
"If I'm trying to summarise what Australians want, this is what they want: they us to be kind, they want us to be compassionate," he told a community cabinet meeting in Rockhampton.
"But they want an orderly migration system so when we're faced with the challenge of people smugglers, let me tell you, this is really tough." (ABC news)