Hope fades for sailors trapped underwater in Hong Kong

HONG KONG, China (CNN) -- Hope has nearly faded for 18 Ukrainian sailors trapped in a tugboat that sank after hitting a Chinese cargo ship three days ago, officials said Tuesday.

Meanwhile, Hong Kong's Marine Department told CNN on Tuesday that it had identified safety problems with the tugboat in 2003. Authorities detained the boat and held it until the problems were corrected, said Daisy Lo, a spokeswoman for the department.

The marine department has not determined whether the safety issues identified in 2003 were a factor in the wreck Saturday that sent the Neftegaz 67 into cold and dark water.

Rescue crews saved seven of 25 crew members after the collision, but 18 others were trapped in the vessel as it slipped beneath the waves, toppled upside down and came to rest into the sea bed, said Roger Tupper, director of the Hong Kong Marine Department. Watch footage of the rescue attempts »

Strong currents and poor visibility have hampered the attempts of divers to determine whether any survivors remain inside the ship, he said.

"Sorry to say that, to date, since we did the first dive on the hull ... we haven't had any response from within the hull of the vessel," Tupper said.

The water temperature is roughly 66 degrees Fahrenheit (19 degrees Celsius), and most people cannot survive for more than 12 hours at that temperature, Lo said. E-mail to a friend

CNN's Anjali Rao contributed to this report.

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