Hundreds more pigs and dozens of dogs have been found dead in central China’s Henan province just weeks after thousands of pigs were pulled from a main waterway in Shanghai.

Chinese health officials and police said they were probing the mysterious deaths of a total of 410 pigs and 122 dogs after their carcasses were found in homes and at farms earlier this week in the city of Yanshi.

Local authorities reportedly suspect the deaths are connected to a nearby chemical factory and have ordered the suspension of operations as part of a police probe.

China’s official Xinhua news agency reported that some village residents complained of a “extremely strong odour” on Monday morning.

No poisonous gases have been found in tests on the air around the village and its drinking water has met quality standards, according to a report on a Henan provincial news website.

A statement from the local government ruled out an animal epidemic or the strain of H7N9 bird flu virus that has spread beyond China’s eastern region. The avian flu virus has so far killed 16 people with 78 reported cases of human infections.