Thirty people remain hospitalized in central China's Hubei Province on Tuesday after an ammonia gas leak in an aquaculture company poisoned over 300 people late on Monday night, according to rescuers.

Over 300 people were rushed to local hospitals and 1,000 others were evacuated after the leak in Deyan Aquaculture Company in Honghu City at 11:30 p.m., firefighters who joined the rescue said.

Thirty people are still under medical observation in hospital as of Tuesday morning. Three of them are severely poisoned, doctors said.

The other poisoned have been discharged after medical treatment.

Ammonia gas was used by the company as a refrigerating agent.