'We are looking at not just a bacteria being active in one herd of pigs but over a fairly wide area, with isolated villages,' said a WHO spokesman. 'Gathering information in that sort of situation is difficult.'

At least 19 people are now known to have died in Sichuan province, the ministry said. None of the infections was transmitted through human-to-human contact, it said.

Victims of the disease suffer high fever, bleeding under the skin and poisoning-related shock, the ministry said.

"According to research and lab test results, experts believe the disease is caused by streptococcus suis," a disease commonly carried by pigs, the ministry said in a statement. "People were infected because they slaughtered and processed sick and dead pigs."

Breeding Ground

The deaths sparked fears of another outbreak of SARS or avian flu, or of a new sickness emerging from China's south, which has been the breeding ground for diseases that jump between animals and humans because of their close proximity.

The latest infections were spread throughout 75 villages and 40 towns near the cities of Ziyang and Neijiang, the ministry said.

"We are looking at not just a bacteria being active in one herd of pigs but over a fairly wide area, with isolated villages," said Bob Dietz, a spokesman for the World Health Organization's regional office in Manila. "Gathering information in that sort of situation is difficult."

While China has been open with information on the outbreak so far, WHO was keeping watch on the situation.

"We see this as a serious situation which bears close monitoring," Dietz said. "This is a disconcertingly high mortality rate."

'Appears to Be Bigger'

China and Hong Kong have seen similar outbreaks in the past but the scales were unknown because surveillance systems weren't as active before, he said.

"Our review of the literature says this appears to be bigger than in the past," Dietz said.

Government officials have been "destroying infected pigs, eradicating contagious channels and treating patients," the China Daily newspaper said.

Farmers have been forbidden to slaughter and process infected pigs, the Health Ministry said.

On Tuesday, health officials in Sichuan wouldn't release details about the outbreak beyond confirming the number of dead and sick.

A woman who answered the telephone at the Ziyang No.1 People's Hospital, where most of the patients were being treated, said they were not allowed to speak to the media.

China was criticized during its outbreak of severe acute respiratory disease for its slow response to international pleas for information. The epidemic killed nearly 800 people worldwide before subsiding in July 2003.

The government is also trying to contain an outbreak of avian flu in its west, where thousands of migratory birds have died in recent weeks.