BEIJING - A school bus carrying 39 people in Fengcheng city, Liaoning province, rolled over on Saturday morning, leaving two children with grave head injuries and causing lesser injuries to another 33 people, according to the local publicity authority.

The bus rolled over while passing a turning point en route to the Central Primary School of Baoshan township at about 7:50 am. A sudden rainstorm left the road frozen and slick, said Lu Xuekun, head of the city government's publicity office.

Lu said that two 7-year-old girls received "grave" head injuries, and they were sent to the intensive care unit of the local hospital. The other 33 students were slightly injured, and they were sent to two local hospitals, Lu said.

"The two severely injured girls are in stable condition after four doctors from Shenyang performed surgery on them," Lu told China Daily on Sunday.

Two of the 33 slightly injured students were treated and released, while the rest remained under observation.

The school bus, which was purchased last year, was qualified to carry 41 people. She said that 39 people, including a driver, a ticket seller, the parent of one student and 36 students, were on the bus.

Wen Xiaohua, the driver, got a license in 2001 and was "experienced", according to Lu. Wen, 33, was still under investigation.

"It's not the only accident on Saturday caused by the rainy weather, which made the road slippery," she said.

Zhang Lihua, a 42-year-old woman whose daughter received a head injury, said that many of the children had similar injuries caused by hitting seat backs.

"My 7-year-old daughter was crying when I arrived at the hospital. She had never encountered such an accident.

"My daughter has no choice but to take the school bus since it is seven and a half kilometers from our home to the school," Zhang said. "We parents have to deal with our work every day and have no time to escort the children to school."

Hundreds of villagers petitioned the local government on Nov 4 over school bus safety, China National Radio reported on Sunday.

Lu refuted the report, saying there was no recorded petition earlier this month concerning school buses.

School bus safety has become a hot topic since an overloaded van carrying students collided with a truck in Gansu province on Nov 16, killing 21 people and leaving 43 injured.