Divers found two bodies on Wednesday inside a Ukrainian tugboat which sank in Hong Kong waters four days ago, a rescue official said, as they searched for 18 sailors thought trapped, according to AFP.

"The two bodies were found inside the vessel," said Tony Leung, a spokesman for the fire department, whose diving team has been conducting the search and rescue operation since the boat sank.

The first body was found around 1:00 am (1700 GMT) and the second at 2:30 am, Leung said, as divers scoured the tugboat for any sign of the sailors.

If all 18 Ukrainians are found dead, it would be the worst marine disaster for decades in Hong Kong, one of the world`s leading ports and maritime centres.

A spokeswoman for Hong Kong`s marine department confirmed that two bodies had been found, but said they had not yet been identified.

The tugboat sank in waters near Hong Kong`s international airport after it collided with a Chinese cargo ship, the Yaohai, in foggy conditions late on Saturday.

The 2,723-tonne tug had 24 Ukrainian crew and one Chinese sailor aboard. Six Ukrainians and the Chinese sailor were rescued.

Marine Department officials have said the crew`s only chance of survival would be if they had found an air pocket, but rescue operations had so far found no signs of life despite repeated dives to the sunken vessel.

Department head Roger Tupper on Monday said medical experts had indicated the missing sailors might survive around 12 hours, given the conditions. Wednesday night would mark 96 hours since the tugboat sank.

Authorities set up a large cordon around the area Wednesday, as two rescue boats floated above the wreckage.

Divers were still making sorties down to the tug Wednesday morning, according to an AFP photographer at the scene.

An inspection six months ago on the Naftogaz-67, which was stuck upside down on the sea bed at a depth of 37 metres (120 feet), had uncovered a catalogue of problems, according to a report in the South China Morning Post.

Citing information from Lloyd`s Marine Intelligence Unit, it said the inspection in the nearby Chinese port of Shenzhen had detailed safety faults, as well as technical and navigational problems on the tug.

In addition, port authorities in Hong Kong had detained the tug twice in 2003 after it had failed safety inspections, the newspaper said, adding that San Francisco port authorities had also detained the ship once that year.

One reason for one of the Hong Kong detentions -- when a ship is forced to remain in port until it is considered safe -- was a failure to provide emergency breathing apparatus, the newspaper said.

Experts said the fact the tug had been inspected 10 times in five years was not unusual.

"It is perhaps unusual to have detentions," Arthur Bowring, managing director of the Hong Kong Shipowners` Association, was quoted as telling the paper.

"That could perhaps be an indication that there could be something wrong."

A delegation from the Ukraine led by vice minister of transport Vasyl Shevchenko arrived in Hong Kong Wednesday and was briefed on the rescue effort, a government spokesman here said in a statement.