An outbreak of African swine fever has been confirmed in piglets being illegally transported through Funing county in China's southwestern province of Yunnan, the farm ministry said.
The case comes amid growing concern that a severe wave of disease in recent months has hit China's hog herd, the world's largest.
Six of the 36 pigs had died, the ministry of agriculature and rural affairs said in a statement late on Tuesday, while six more in the truck were sick.
Beijing reports few disease outbreaks on Chinese farms but some analysts have recently estimated that about a fifth of the breeding herd in northern China was affected over the winter.
Average piglet prices are now 91 yuan ($14) a kg, up 11% on a year ago.
African swine fever is usually fatal to pigs, but recent studies have identified some less lethal variants circulating in China