Chief minister Chow Kon Yeow said the latest cases involved two farms in the Seberang Perai Tengah district and two more in Seberang Perai Selatan.

He said the outbreak was showing no signs of abating and is likely to worsen without an effective vaccine.

“Previously, seven farms were affected, namely two in Seberang Perai Tengah and five in Perkampungan Valdor in Seberang Perai Selatan. Currently, the Penang veterinary services department is carrying out sampling work in (other) pig farms.

“So far, 4,000 pigs in three farms (infected with ASF) have been culled, and culling will continue in other farms,” he told reporters here.

Last Friday, Penang declared the ASF outbreak a disaster after cases were reported in seven more commercial pig farms involving 25,000 animals in the two districts.

Meanwhile, Penang police chief Shuhaily Zain said the police had mounted roadblocks to control the movement of live pigs or pig carcasses in areas where the outbreak was detected, to ensure the disease does not spread to other areas.

According to state veterinary services department data, there are 124 pig farms in Penang with a total of 267,348 pigs.