Navigation of China's Three Gorges ship lock resumed in both directions at around midday Monday after a 37-hour halt due to foggy weather.

More than 500 passengers on board five ships had been evacuated by 1 p.m. since navigation at the five-tier ship lock resumed at 11:30 a.m., when the fog faded and visibility returned to navigational requirements, the Yangtze River Three Gorges Navigation Bureau said.

Vegetables and grains were given to passengers for food.

About 80 cargo ships out of more than 200 vessels, stranded at the Three Gorges Dam area since the thick fog rolled in late on Saturday, had passed the ship lock by 5:20 p.m., the bureau told Xinhua.

All the remaining vessels were expected to pass through the lock by late Tuesday as each pass took about three hours.

A high pressure, weak wind, continuous rainfall since Saturday, and the special gorge terrain that hampers the diffusion of vapour, jointly contributed the formation of the fog, said Zhou Yuehua, an expert with Hubei Provincial Meteorological Bureau.

Weather forecasters say the sky at the dam area will be clear on Tuesday, but it did not exclude the possibility that fog may reoccur.

It is extremely difficult to forecast foggy weather, especially in the mountainous area, according to Ji Yujian, deputy director of the Three Gorges Navigation Bureau.

The Three Gorges -- the Qutang, Wuxia and Xiling gorges -- extends about 200 kilometers on the upper and middle reaches of the 6,300-kilometer Yangtze, China's longest river.

China launched the Three Gorges hydropower project and water control facility in 1993 with a budget of 22.5 billion U.S. dollars.

A 185-meter-high dam was completed in 2006. The five-tier ship lock was commissioned in 2003.

Workers have so far completed installation of 21 generators. The project's 26 turbo-generators are designed to produce 84.7 billion kwh of electricity a year after its scheduled completion this year.

(Xinhua News Agency, March 18, 2008)