Heavy fog has stranded vessels at the Three Gorges area for 24 hours -- the longest period of time since it was built in June 2003 -- as of Sunday night, a local waterway official said.

"The thick fog, engulfing the dozens of kilometers of areas from the Three Gorges to the Gezhouba Dam, is rarely seen here," said Ji Yujian, deputy director of the Three Gorges Navigation Bureau.

The operation of the ship lock has been canceled and over 150 vessels were stranded till 23:00 PM on Sunday, Ji said.

Thick fog engulfed the dam area at 22:40 PM on Saturday and left the visibility of both the two directions less than 500 meters, Ji said.

Thirty-eight southbound and northbound vessels were navigating near the ship lock when closures began at Saturday night, including five passenger ships with more than 500 passengers aboard, Ji said.

The administrative bureau started to broadcast the causes since the closures began and send vegetables and foods to the stranded on Sunday night, Ji said.

The fog faded a little at 19:40 PM on Sunday.

However, the fog became dense again at 21:00 PM and reduced the visibility to less than 200 meters. Twenty vessels, including two ships with 200 passengers, were still stranded in the lock, the official said.

"Almost all the colleges are working at the site. Passengers expressed their understanding of the nature disaster and cooperate pretty much," Ji said.

Cloudy days are expected to continue in the area and the temperature will be between 11 and 20 centigrade degrees. Ji said the time to reopen the ship lock cannot be predicted so far.

(Xinhua News Agency March 17, 2008)