Local authorities said Friday that pigs and dogs that were found dead in a village in central China's Henan Province on Monday died from respiratory failure due to inhaling toxic gas.

A total of 410 pigs and 122 dogs were found dead Monday morning in the village of Dongtun in the city of Yanshi.

The No. 1 Hospital affiliated with the Henan University of Science and Technology said test results showed that the animals died from respiratory failure.

A local medical manufacturing plant has been under investigation for allegedly causing toxic gas leaks. However, the gas that killed the animals has not been identified and it is unknown whether the plant had any part in their deaths.

Some villagers claimed that the factory has been emitting a strong odor for more than ten years. They said the smell was particularly strong Monday morning.

Test results from local environmental authorities indicate that the area's air and drinking water are clean.