The fog was so bad in the city that an elderly couple reportedly accidentally fell into a lake on their way to morning exercises at Beijing's Summer Palace.

They were soon rescued by others, reports said.

Weather forecasts said the fog density reached the maximum degree of measurement yesterday.

Meteorologists said the air flow in the region has been nearly deadlocked over the past few days, and that combined with increasing temperatures and humidity, created the heavy fog.

Forecasters said the fog is expected to clear out tomorrow when a cold air front from the Xinjiang Uygur Autonomous Region enters North China.

Statistics from the Beijing environmental protection authority said air pollution in the capital city reached five degrees, making it extremely polluted. The only other time the city reached such polluted levels was during the huge sandstorms that rocked Beijing this past spring. The weather is very harmful to people's health, experts said.

Doctors with the Beijing No 6 Hospital warned that the fog creates good conditions for bacteria to proliferate. People should avoid going outdoors, they added.

The fog blocked Beijing's air traffic beginning late Monday and Beijing Capital International Airport was forced to close.

More than 66 flights were delayed and more others set to take off and land here were delayed, cancelled or transferred to other airports.

Passengers were advised to return home and await further notice.

Airport authorities said yesterday that the fog density made the airport unsuitable for operation. All blocked flights could be cleared by this evening, they added.

Road traffic was not severely affected, experts said, but many automobiles were traveling at low speeds.

Taxi driver Zhu Jiangguo said local radio broadcasts had repeatedly warned about the fog and the poor traffic conditions in city since Monday evening.

"Several of my customers said they parked their cars at homes and went to work by taxi,'' Zhu said.

He said the decreased number of automobiles on the roads helped maintain relatively smooth traffic flow.

Beijing's major expressways to nearby provinces were also closed yesterday. Traffic administrators said they would gradually reopen these roads after the fog lifts. Motorists wishing to leave Beijing are urged to call 122 for road condition consultation. Authorities will also release traffic conditions via local radio stations regularly, they said.

(China Daily December 4, 2002)