By Peter Brieger

HONG KONG - Two men have died and six are missing after two commercial vessels collided Tuesday off the east coast of Hong Kong, the city's marine department said, as it expanded an air and sea rescue operation.

At about 3:15 am, police received a report about a sand barge with 14 crew on board colliding with a container vessel with nine crew, a department spokesman told AFP.

Hong Kong's fire services dispatched five rescue boats with about 100 crew to the scene in a frantic bid to find the missing mainland Chinese seamen. One seaman was discovered dead when his colleagues were plucked to safety, while another's body was found Tuesday afternoon, the spokesman said.

The capsized sand barge sunk below the choppy waters of the South China Sea, but the vessel had not touched the sea bed, a marine department spokesman told a press briefing Tuesday.

"The rescue divers are risking their lives," he said.

"They're trying to get down to the sunken vessel, but the current is extremely strong and the ship is not completely grounded to the sea bed."

The spokesman declined to say what might have caused the accident or comment on the likelihood of finding the missing seamen alive.

"The weather was not good and visibility was poor at the time of the collision," he said.

"There were big waves, but it is normal for large ships to operate under those conditions."

The search would continue for another day or two, the spokesman said. The dead and missing crew were all from the sand barge, with another six crew from the same vessel treated in hospital.

The container vessel has been taken back to port with its nine crew all safely rescued.

The deadly accident comes less than a week after another barge appeared to be sinking in the middle of Hong Kong's famed Victoria Harbour, setting off panicked calls to emergency services.

A fire boat rushed to the scene but was told that the vessel was intentionally submerged to conduct engineering work.

In January, a Hong Kong court jailed four seamen for the deaths of 18 Ukrainian sailors killed when two vessels collided in 2008, the city's biggest maritime disaster in recent decades.

The four were convicted of endangering the life of others at sea after the court concluded that the collision of Ukrainian tugboat Neftegaz-67 and Chinese cargo ship Yaohai was due to their "deliberate omission to act."

Yuriy Kulemesin, captain of the tugboat, was sentenced to three years and two months imprisonment.

The other three defendants - Yaohai captain Liu Bo and pilots Tang Dock-wah and Bruce Chun - were given terms of between 28 months and three years.