The death toll from a devastating flood that swept through an elementary school in northeastern China has risen to 91, including 87 elementary school students.

The flash flood swamped the Shalan Village Central Elementary School in Ningan township, Heilongjiang province, on Friday afternoon, leaving many students aged from six to 14 with no escape route as waters rose up several meters in the school yard.

Local officials refused to comment on the disaster, but the government-run Dongbei Website said the toll had risen to 91 as of early Sunday morning, up from 64 on Saturday.

Locals painted a picture of total chaos at the one-storey school after landslides in the upper mountainous reaches resulted in torrents of muddy water and debris engulfing the school yard, leaving little chance for the youngest children to survive.

"I think the death toll could rise to as many as 100. According to what people are saying none of the first and second grade students survived," a young mother named Zhao told AFP.

"Some teachers were saying that at the time of the drownings, the water was several meters high, so the youngest children would not have much of a chance."

State press said 352 students were enrolled in the school, with Zhao saying that at least 100 were in the first and second grades and between six and eight years-old.

"My mother is 60 years-old and has lived here all her life, in all her years she has never seen anything like this," Zhao said.

"From the time it started to rain, until the time the flash flood came lasted only about 30 minutes."

The school is located at a low point in a mountainous valley that runs along the Shalan River.

"In the past, Shalan village was known as Shalan ditch, the village itself is in a deep gully," former county head of Ningan County Jing Dianyuan told Xinhua news agency.

"The school was built in the lowest point in the village," he added.

Seven of 18 villages in Ningan region have been damaged by the floods, with 55 homes washed away and 1,800 villagers stranded by the waters, Xinhua said.

Between 150 and 200 millimeters (six to eight inches) of rain fell on the area during a 40 minute period leading up to the flooding, the report said, citing local officials.

"The reasons for the flood was due to a sudden and huge amount of rain hitting a small area over a short period of time and causing landslides," Dong Shuhua, head of the Heilongjiang water resources bureau, told Xinhua.

"This kind of rain happens once every 200 years and is very difficult to prepare for."

Heilongjiang's Governor Zhang Zuoji and other senior officials were directing rescue operations at the scene, about 450 kilometres (280 miles) southeast of the provincial capital Harbin. Searchers continued looking for missing villagers, Xinhua said.

The disaster is the latest in a series of tragedies caused by recent heavy rains in China. State media reported on Tuesday that at least 255 people were killed in floods and storms in southern central China in May, the start of the country's rainy season.

Thousands of people perish every year from floods, landslides and mudflows in China, with millions left homeless, and officials have warned this year's floods could be worse than usual.

The China Meteorological Administration warned last month of an "apocalyptic" summer of severe drought and floods.

PHOTO CAPTION

Chinese soldiers search for victims near a flood-stricken school in Shalan, northeast China's Heilongjiang province, in this picture taken on June 10, 2005. (Reuters)