Australian Customs and Border Protection said the boat capsized about 70 nautical miles off the island Tuesday night, CNN reported. The agency said the Australian Navy assisted by an air force plane managed to rescue at least 144 people. It was not known immediately if more people were missing.
The nationalities of the boat's occupants were not available. CNN said Australian authorities described them as "asylum seekers."
Christmas Island, between Australia and Indonesia, is a drop off point for those involved in smuggling migrants, the BBC reported.
CNN said the rescue effort, which also involved other vessels that responded to radio requests for help, went on until 9:30 p.m. before being called off.
The report said before overturning, the boat had requested help from the Australian patrol vessel HMAS Albany, but bad weather prevented a boarding.
"HMAS Warramunga rescued 76 people from the water and HMAS Albany rescued 68 people from the water. Tragically, four deceased persons were recovered," Australian Customs said in a statement.
"Recovering 144 people in the conditions they had yesterday was extraordinary work," David Johnston, commander for Australia's Border Protection Command, told the BBC.
The report said such trips by those seeking to come to Australia are common. However, it said several of these boats have disappeared in recent months.