More survivors found after asylum boat sinking

The number of asylum seekers found alive after their boat sank off Indonesia has increased to more than 50, but at least 90 are still missing.

Fifty-five asylum seekers have now been plucked from the sea after their boat sank near the coast of Java.

Three of the survivors have serious injuries but are in a stable condition on board the Australian Navy boat HMAS Maitland.

The ABC has been told that one person may have suffered a shark bite.

Another six of the survivors have been taken to the Indonesian port city of Merak for medical attention.

The search and rescue operation has now been scaled back until first light on Friday.

Several boats will remain in the area overnight but authorities say it will be hard to find further survivors in the dark.

Up to 150 people are believed to have been on board the boat, which first made distress calls on Wednesday morning.

HMAS Maitland, a Defence plane and several merchant ships were at the scene on Thursday, about 40 nautical miles from Java.

An Australian plane dispatched from Christmas Island also searched the area on Thursday but was forced to return because of fuel concerns.

Meanwhile, the Indonesian search and rescue authority, Basarnas, has said it regrets initially calling off the search for the missing asylum seekers.

On Wednesday Basarnas sent helicopters and boats to the area, but when the choppers returned without having spotted any survivors or wreckage, the search was called off altogether.

Spokesman Gagah Prokoso says the organisation regrets calling off the rescue, but he says they could not find any evidence of the boat and they are not adequately equipped for big ocean search and rescue operations.

He says their helicopters are too small to do wide-ranging searches and their rescue boats are not big enough for the ocean.

Home Affairs Minister Jason Clare has defended the initial search by Indonesian authorities, rejecting the assertion that crucial hours were lost.

"Don't underestimate how difficult this task is; don't underestimate how big the sea that we're searching is," he said.

Three other boats carrying 500 people are known to have sunk on a similar route in recent years.

See AMSA maps of incident - 1 and 2