Hopes have been raised that another, large group of asylum seekers may have survived the tragic sinking of a people smuggling vessel three days ago and are sheltering on an island off the coast.

Police are taking seriously the information that an asylum seeker called his family in Pakistan late yesterday, saying he was with the group of people, some of whom were injured.

Armaghan Haider, an Afghan survivor of the disaster, said the news provoked a wave of optimism among survivors staying at the Grand Mansion hotel in Blitar, especially as it came just after 13 people were discovered yesterday on another island, Nusa Barung, some 200 kilometres from where the vessel laden with about 250 asylum seekers capsized on Saturday.

At least 47 people on the boat are now confirmed to have survived.

Mr Haider said the man who contacted his family was named Farhan, and urged them to get in contact with Indonesian authorities.

"He was not among the 13 people," said Mr Haider. "He called his family and told [them] that 'I'm safe. Among me is a lot of people who are safe. We are trapped on some island. I don't know where it is. My neck, my hand, my nose, everything is broken but a lot of people are still alive in this island'."

The information could not be independently verified. The Indonesian mobile phone number that Farhan' gave his family was out of range or switched off when called by Fairfax.

However, a police source said the information is being followed up with the utmost urgency. A Jakarta-based refugee advocate who knows many of those on the boat also confirmed that the information was relayed to him last night.

Two Indonesian men, believed to be crew of the vessel, were also found on a beach in East Java yesterday. They are in a hospital in Malang and being interviewed by police. It is understood they claim they are just fishermen who were tossed from a small boat.

However, police are treating their denials with scepticism.