A thick fog engulfed Beijing last night, reducing visibility to virtually zero and leaving commuters struggling to stay out of harm's way. The fog, which is expected to continue blanketing much of the city today, coincided with a heavy snowfall which made roads slippery and slowed traffic to a snail's pace. Visibility in northern suburbs near the Beijing Capital International Airport was down to virtually zero and drivers travelling on the fifth ring road and the airport expressway were forced to flash their emergency lights as they inched forward. The China News Service said the Beijing Meteorological Bureau raised the yellow traffic alert yesterday morning, but the warning was apparently lost on most drivers with police reporting more than 1,000 accidents before noon alone. On just one short section of the highway between Beijing and Shijiazhuang , more than 20 cars were involved in a pile-up. Some drivers said the visibility was so poor that it was impossible to see traffic lights, and almost everyone was driving blind. A police assistant was quoted on the qianlong website as saying that so many traffic policemen had been sent out to handle accidents yesterday that even he had to help. 'All traffic policemen are out dealing with accidents everywhere,' the assistant said. 'I heard on police radio that roads are so slippery that all officers have been deployed. 'On just one small section, there have been more than 10 accidents.' An employee of the Beijing Metrological Bureau last night would not give details of the weather outlook, except for saying that a thick fog had first appeared in the Changping area. Calls to the bureau's 24-hour hotline were not being answered last night. An airport employee said a number of incoming flights had been diverted to other nearby cities last night, but would not say how many had been delayed or cancelled yesterday. However, the qianlong website said more than 50 flights were delayed yesterday morning. The China News Service report said most flights in and out of Beijing airport were delayed by at least 30 minutes. Airport staff were seen removing snow from planes, but the airport remained open for the day.