Hohhot (China), Aug 5 (Xinhua) Over 200 people fell ill Wednesday after ammonia gas leak at a pharmaceutical plant in north China's Inner Mongolia Autonomous Region, the authorities said.

Officials at Hongshan district said 21 people were hospitalised Wednesday afternoon and 181 others remained under observation. No one died in the ammonia leak.

The leak occurred at 8.40 a.m. when a truck carrying 30 tonnes of liquid ammonia was unloading at the factory of Chifeng Pharmaceutical Group. A pipe suddenly burst during the unloading.

Those affected are workers in the factory, emergency responders and residents living nearby.

People within 2 km of the leak were evacuated.

An initial investigation suggested that the leak was caused by workers failing to operate the equipment properly and old pipes.