BEIJING - More than 50 cars were involved in a series of accidents caused by a sudden heavy snowfall on a freeway in East China's Shandong province on Thursday, leaving two people dead, local authorities said.

Eleven people were injured in the accidents, at least three of them seriously. All of the seriously injured people in the accidents were taken to the local hospital for treatment, said Pan Yuan, a publicity officer of the Weifang fire department, which took part in the rescue. Six of the injured chose not to go to the hospital.

Rescurers carry an injured after a mass pile up involving more than 50 vehicles on the Weifang section of Qingdao-Jinan highway in Shandong province, Dec 8, 2011. [Photo/Asianewsphoto]

"It's the most serious freeway accident I've ever seen," Pan told China Daily on Thursday afternoon.

Dozens of vehicles were involved in the accidents, which occurred on a 112-kilometer stretch of the freeway near Weifang. A truck hit a bus on the Weifang section of the Jinan-Qingdao Expressway.

The snow began falling at 11 am, making the road slippery, Jinan-based Dazhong Daily reported on its website.

The Shandong provincial department of public security told the media that two people had been killed, but no details were released. Police officers and officials from local health departments also joined the rescue.

Several cars slid off the road into ditches along the freeway and got trapped in the snow, photos on the Dazhong Daily website show.

The Weifang fire department dispatched 16 rescuers and two vehicles to the scene and the rescue work continued until late in the afternoon, Pan said.

The accidents caused a traffic jam more than 4 km long, Pan added.

The traffic police have closed nearly 20 entrances to the freeway to prevent more accidents on the slippery road, according to a notice on the Shandong Hi-speed Group's website at 5:30 pm on Thursday.

The Jinan-Qingdao Expressway, built in 1993, has two lanes in both directions. Because of the sometimes heavy traffic, the Shandong provincial department of transport has planned to expand the road to four lanes in both directions by the end of 2015, according to a report by the Jinan-based Qilu Evening News in December 2010.

Zhao Ruixue in Jinan contributed to this story.