Christmas Island lies off Australia’s north-west coast. It is closer to Indonesia than Australia, and is targeted by asylum-seekers hoping to start a new life in Australia.
The Australia Maritime Safety Authority AMSA said the boat sank in Indonesian Waters, 120 nautical miles (220km) north of the island.
Indonesian and Australian rescue vessels were in or heading to the area.
Jo Meehan, a spokesperson for AMSA, said that an Australian customs surveillance aircraft had alerted them to the capsized boat.
At least 40 people have been seen on the hull of the vessel, but police said many others were feared to have died.
“There were about 200 refugees on board we think. Currently there’s about 40 on the hull and the rest are in the water,” said Western Australia police commissioner Karl O’Callaghan.
“Some of the very early reports suggest that up to 75 people may have drowned, but I do stress that they are unconfirmed at this stage,” he said.
These boats are notoriously over-loaded and often in poor condition. In December 2012 about 50 asylum-seekers died when their boat crashed on rocks.
Patrol boats are in the area and with night searching capabilities will aid in the rescue.
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