A local resident purchases pork at a farm produce market in Shanghai, on Feb 15, 2020. (Photo: Xinhua)

The Ministry of Agriculture and Rural Affairs has received 13 reports on African swine fever on the Chinese mainland since March, a drop from 24 in the same period last year, a senior official told a news conference on Sunday.

According to Wei Hongyang, deputy director of the ministry's animal husbandry and veterinary bureau, 1,313 infected hogs have been culled since March, compared to 240,200 during the same period last year.

Investigations showed that most cases were related to illegal trading and transportation, such as transporting hogs without quarantine inspection certifications in unregistered vehicles.

Overall, the African swine fever is under control, but the ministry remains on high alert.

Starting April 1, the ministry joined hands with authorities of public security and transport in a 60-day campaign against illegal transportation of pigs, as risks increased after enterprises nationwide gradually resumed operation, including hog-production companies.

"We have been monitoring online trading platforms for hogs and sent inspection teams to some southern provinces deemed as major places with the fever problem," he said.