JAKARTA - AN INDONESIAN ferry that sank on the weekend may have been carrying 103 people more than those listed on its manifest, officials said on Thursday, raising the prospect of a death toll topping 330.

But officials still could not say whether the ferry was overloaded when it set sail from Sulawesi island to Borneo on Saturday.

Some 250 passengers and 17 crew were listed on the 700-tonne Teratai Prima's manifest. Only 35 have been found alive since the ferry sank in heavy seas whipped up by a tropical storm in the Makassar Strait early on Sunday.

'Based on reports from relatives there were at least 103 passengers who were not listed on the boat's manifest,' transport ministry spokesman Bambang Erfan said.

He said that while this could mean as many as 370 people were on the ferry when it left Pare-Pare port, western Sulawesi, the numbers could also be misleading.

'We're investigating whether they used different names like nicknames or there were more passengers than the number registered,' he said.

'We haven't arrived at any conclusion that the boat was over capacity,' he added.

Another official was quoted in The Jakarta Globe daily as saying there was 'something strange' about the passenger list, which made no mention of people under 15 years of age.

President Susilo Bambang Yudhoyono has ordered a tough investigation into the ferry disaster, the worst in Indonesia since a ferry sank in 2006 killing 500.

A probe is already under way amid claims that the ferry's captain, who survived, ignored storm warnings, that port authorities allowed the ferry to be overloaded and that it was not properly equipped with safety gear.

Navy, air force and police personnel were still searching the Makassar Strait for survivors on Thursday but officials have said they believe most of the missing passengers and crew went down with the ferry. -- AFP