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JAKARTA - An Indonesian ferry that caught fire last week, killing at least 42 people, sank today as officials and journalists on board scrambled for safety.

At least three people were missing after the incident off Jakarta, witnesses and Indonesian media said. Lativi television said one of its cameramen had been killed.

The Levina I was on its way to Bangka island off Sumatra packed with hundreds of people when it caught fire soon after dawn on Thursday 80 km from Jakarta's Tanjung Priok port.

Yesterday the scorched hulk was hauled to a point about six 10 to 16 kilometres from the main port in Jakarta and put at anchor, a spokesman of the Indonesian navy's western fleet said.

"It had been anchored at the time, but it was tilting on one side," he said.

More than 10 people -- forensic police, transportation safety officials and journalists -- had boarded the ship today when it began to sink, media reports said.

"Some of us were given life vests, but others were not wearing (them). Three people have not been found, and two people are in critical condition," SCTV reporter Agus Faisal Karim said over his own broadcaster.

"We are safe, we are not injured, but all of us panicked. Some of us were in the water for a long time," he added.

State news agency Antara put the number of missing at five, a journalist, two transportation safety officials and two forensic police staff, and said three others had been hospitalised.

The known death toll from the original accident had jumped from 20 to 42 on Sunday.

"Fishermen found 21 bodies today," Panji Nirwana of the national search and rescue agency told Reuters. Rescuers later found one more body, another search and rescue official said.

Navy rescue team head Colonel Didin Zainal Abidin told Reuters the search for more victims and survivors of Thursday's disaster was continuing.

About 300 of those who were on board are known to have survived, but how many were still missing was clouded in confusion because a number of passengers were apparently not listed on the official manifest.

Earlier on the weekend, nine navy ships and two helicopters were involved in the search.

Some estimate scores of passengers could still be missing based on statements from individuals who say they had relatives on the ferry. Some people might also have been saved without their rescue having been recorded.

It is common in Indonesia for people to sneak on to ferries or bribe crew to let them on for less than the price of a ticket, meaning their names do not show on the official manifest.

Preliminary findings suggest the fire started in a lorry carrying inflammable chemical cargo on the lower deck.

Many passengers hurled themselves off the blazing 27-year-old Japanese-built vessel into the sea to escape the flames and searing heat.

Ferries are a popular means of transport among the 17,000 islands of Indonesia, where sea connections are cheaper and more available than air routes. But safety standards are not always strictly enforced and accidents occur fairly often.