ZHENGZHOU, Sept. 18 -- A synthetic ammonia leak at a chemical plant in central China's Henan Province poisoned 20 residents in a nearby village on Friday morning, local authorities said.

The government of Pingdingshan said the leak happened at about6:30 a.m. at Henan Zhonghong Coal Chemical Company where 300 kg of synthesized ammonia leaked from a cracked pipe.

The poisoned villagers, including five in serious condition, have been sent to hospitals.

The government said they detected no ammonia when monitoring air quality near the site at 9:20 a.m..