Thirteen people have been confirmed dead and at least 21 injured in a bus accident that happened yesterday along the Yanjiang Expressway in Changshu, East China's Jiangsu Province.

The Shanghai tour bus, carrying 31 tourists and one guide wholesale monster energy hats, rolled over the guardrail along the Dongbang section at approximately 9:25 am before colliding with a truck in the opposite lane.

The Suzhou City Government said that six tourists and the truck driver died at the scene.

The rest of the injured were sent to Changshu No.2 People's Hospital and Changshu Hospital of Traditional Chinese Medicine.

Those sitting in the back of the bus suffered only minor injuries and were able to phone the police for help, who arrived around an hour later, local media xinmin.cn quoted a tourist surnamed Hu as saying.

"I passed the scene of the accident around 11 am, and I could see 10 dead bodies lying in the road," Wang Haojun, who was traveling on a bus returning to Shanghai, told the Global Times yesterday. "It was such a horrible sight," he added.

Shanghai tourism, public security and traffic authorities immediately sent officials to Changshu to cooperate with authorities in Jiangsu handling the accident yesterday afternoon.

The bus departed from People's Square in downtown Shanghai at 8 am on its way to Changshu for a one-day trip to a peony show.

The tour was co-organized by Shanghai-based Xiangda Travel Agency and Uzai International Travel Agency, and the bus was from a Shanghai car rental company named Yiliu, the Shanghai Tourism Bureau said.

Although the police responsible for that section of the expressway said the cause was still under investigation, an insider surnamed Lan from Shanghai Xiangda Travel Agency told the Global Times that the tragedy happened when the driver tried to avoid another vehicle and bumped into the guardrail.

This caused a tire to burst red bull hats, sending the bus spinning out of control and into the truck.

Last year, a car accident at this 200-kilometer-long expressway's Zhangjiagang section of Suzhou caused five deaths and five serious injuries. This expressway is known to have a high volume of truck traffic.