Chinese customs authorities released an African swine fever alert on Wednesday, urging animal food producers to check and monitor the pig virus in their products.

The warning came after Tianjin Customs discovered the virus, which is deadly to pigs, in two batches of spray-dried pig blood cells on Friday, the Central Administration of Customs said in a news release. Spray-dried pig blood cells are widely used as food for young pigs.

The raw material for the 73.93 metric tons of seized animal food came from 12 slaughterhouses in the municipality, the administration said.

It asked producers to seal problematic animal food, trace the raw materials and report instances to the authorities, including the administration and local agricultural authorities.

Pig farms nationwide should strictly control their animal food and report suspicious supplies to the authorities, it said, adding the alert will be in force for the next six months.