BEIJING -- The Chinese government on Friday called a bus fire last month that killed 10 South Korean children in China an act of arson, the South Korean Embassy in Beijing said.

The Chinese foreign ministry notified the South Korean Embassy of the outcome of an investigation into the cause of the incident on May 9, when a school bus carrying 11 kindergarten students and a teacher caught fire inside the Taojiakuang Tunnel in Weihai, a city in the eastern Chinese province of Shandong.

Along with the 10 South Korean children and one Chinese child, the bus driver and their teacher also perished. The students attended a kindergarten affiliated with an international school that largely caters to Koreans.

Chinese media have reported that the pupils were five South Koreans and six Chinese based on an announcement by the Weihai municipal government. But the South Korean Embassy said it is believed 10 were South Korean, including those with dual citizenship.

According to the investigation, the driver, Cong Weizi, was in a feeble-minded state when he set the bus on fire after he rear-ended a preceding vehicle.

The Shandong provincial police agency told a press conference at a Weihai hotel the same day that Cong bought a lighter and gas, placed them in the bus and set it alight on the day of the bus fire, one day after he was dissatisfied because the school gave him a dismissal notice.

During the press conference, the police agency's vice chief, Wang Jincheong, said the cause of the Weihai school bus incident was the result of the driver's arson, and traces of the lighter and gas bought by the driver were found.

"The driver seemed to have spite against the school because he was terminated by the school the previous day," Wang added.

The Chinese police believe the fire was a premeditated crime, saying CCTV footage on the bus and video clips, taken from black boxes in about 280 vehicles passing through the tunnel at the time of the fire, showed the fire starting from behind the driver's seat.

They also secured video footage in which Cong appeared to open a gas container hesitantly when he boarded the bus. His purchase of gas for the diesel-powered bus and a lighter in spite of being a nonsmoker strengthened the police's belief that Cong planned the crime in advance.

But the bereaved family members of the killed children said they cannot accept the investigation results.

"There are many doubtful aspects regarding the announcement," said Kim Mi-seok, the leader of the families' group. "The Chinese authorities appear to have been trying to hold the driver responsible." 

Kim objected to where the police claim the fire started, saying photos and video clips on the scene showed the right side of the vehicle, not the driver's seat, first catching fire.

In Friday's notification, the Chinese ministry and the Shandong provincial government also expressed their willingness to make the utmost efforts to compensate the bereaved families of the victims.

A joint team of Chinese police sent forensic investigation organs in Tianjin, Yantai and Qingdao, evidence collected at the scene to conduct the probe. In order to find out what caused the fire to happen, the team also utilized scientific methods by re-enacting various situations involving vehicles, roads, drivers and weather.

It took just under one month to discover the cause of the incident as the Chinese leadership, including President Xi Jinping, showed concern.(Yonhap)