The World Health Organization (WHO) says it is too early for China to say if a pig-borne disease that killed at least 30 people is under control.  A WHO official says China did a good job of responding to the disease, but more investigating and testing needs to be done.

China's Health Minister, Gao Qiang, has called on local officials and health workers to step up inspection work and prevent the transport of sick pigs.

Mr. Gao says the government has "preliminary control" of the bacterial disease that originates in pigs and has infected dozens of people.

Bob Dietz is a spokesman for the World Health Organization.  He says although the outbreak seems to be localized in one province of China, the disease has spread to more towns in the area.

"As we see the numbers continue to rise, both in terms of the apparent number of cases and the apparent numbers or deaths, that when you're in a situation like that, to say that its under control does seem premature," said Mr. Dietz.

China's Ministry of Health said the death toll reached 31 people by Thursday afternoon, four more than the day before.  There were also 21 new infections, bringing the total confirmed or suspected infections to more than 150. 

The disease, which was discovered in June in China's southwestern Sichuan Province, infected farmers and pig-slaughterers who came in contact with infected pigs.  So far there have been no cases of it spreading from human to human.

The WHO says it is not disputing preliminary laboratory tests in China indicating the disease is caused by a known pig-borne bacteria. 

Mr. Dietz says the Chinese government is doing a good job responding to the outbreak and sharing information with the World Health Organization. 

China's state media say roadside checkpoints have been set up to keep sick pigs or infected meat from spreading around the country.  Thousands of health workers have been sent to farming households around the city of Ziyang, where most of the infections were found, to inspect and register every pig in the region.