(CNN) -- Australian authorities ended their efforts to find survivors Friday after a boat carrying scores capsized off the coast of Indonesia this week.
An Australian naval ship and four merchant vessels rescued 55 people in an area west of the Indonesian island of Java, the Australian Maritime Safety Authority said. But many more others may have perished in the sea.
The authority said it was halting further efforts following medical advice that "there is no realistic prospect of survivability." One body was recovered during the rescue operation.
Rescuers had been searching for survivors since Wednesday, when Australian authorities received a call from someone aboard saying the vessel was having engine trouble. The caller said it had about 150 people aboard, presumed to be asylum seekers.
The survivors, including at least three with injuries, were being taken to Merak, Indonesia, Australian authorities said.
Several ships carrying asylum seekers in Australia have run into trouble in the waters between Indonesia and Australia in recent years.
Vessels often head for Christmas Island, a remote Australian territory closer to Java than to the Australian mainland.
Dozens of people are believed to have died after two ships capsized near Christmas Island in June. More than 200 people were rescued from those accidents.