JAKARTA (REUTERS, DPA) - Indonesian rescuers were battling high tides and strong winds on Friday (Aug 2) in a search for 31 people missing after a fishing boat sank in waters off Borneo island, killing at least four, an official of the search and rescue agency said.

There were 37 people on board the vessel, four of whom had been found dead, while two had survived, agency spokesman Iman Saputra said by telephone.

"Rescue efforts will go on for the next four days. The obstacles are high tides and strong winds," said Saputra, who is based in the city of Banjarmasin, the capital of South Kalimantan province, near the site of the sinking.

The vessel had left the town of Pekalongan on Java island three days ago before running into trouble, Saputra said, adding that the agency had deployed 35 people to hunt for those missing.

The head of the rescue agency in Banjarmasin said the agency was only alerted on Friday because the boat did not send a distress signal.

"We have equipment to detect a distress signal from a boat but we did not receive any," Endrow was quoted as saying by Kompas.com. "Maybe the equipment on the boat was damaged," he added.