Officials had earlier said the Ukrainian sailors could have found air pockets that would enable them to survive, but divers did not hear any noises when they knocked on the capsized boat on Sunday.
Salvage crews have been attempting to get the NefteGaz 67 to shallower waters to make the rescue work easier, but strong currents have hindered the move, a government spokeswoman said.
Seven of the NefteGaz's 25-strong crew, including the captain, were rescued and were being treated in local hospitals.
The 80-metre tugboat sank rapidly after the accident in waters northwest of Hong Kong's outlying Lantau island.
The cause of the accident was not immediately clear but media reports had the captain of the tugboat accusing the Chinese vessel of refusing to give his ship the right of way.
|Rescue efforts continue in hopes that the |
sailors found air pockets [AFP]
"He had received from the controller permission to pass. The Chinese cargo ship should have let it pass, but it did not do that," said Anatoly Prisiazhnyuk, the president of the energy company Chornomornaftegaz which owns the tugboat.
The vessel had been travelling from the southern Chinese city Shenzhen to an oil field south of Hong Kong.
The Chinese-registered cargo ship Yao Hai suffered only minor damage in the collision.