HANOI (Reuters) – African swine fever has spread to Thanh Hoa province, south of Hanoi, the fourth Vietnamese province to report infections, state media said on Monday.

Authorities have culled 226 pigs at a farm in the province, 160 km (100 miles) south of Hanoi, after samples take from dead pigs there tested positive to the virus, according to a report in the Nong Nghiep Vietnam newspaper, run by the Ministry of Agriculture.

The newspaper said earlier Monday the virus had also been detected in Haiphong to the east of Hanoi.

(Reporting by Khanh Vu; Editing by Kim Coghill)