A 42-year-old worker died allegedly after an ammonia gas leak at a Haldiram's building in the city, while more than 300 others were evacuated from there on Saturday, officials said.

The leakage was reported around 12pm, prompting immediate deployment of police force, firefighters and the National Disaster Response Force (NDRF), they said.

There are two adjoining units of Haldiram's in the building, one was the production unit and the other was its cooling or the maintenance unit, an NDRF official said.

'The gas leak had occurred through the valve of one of the four ammonia condensers in the maintenance unit where around 22 people were working and evacuated. One of them was taken to a hospital, where he died later,' NDRF assistant commandant Anil Kumar Singh told PTI.

The man who died has been identified as ammonia operator Sanjeev Kumar, he said.

More than 300 other workers were in the production unit and they were also evacuated immediately and the building marked isolated for the time being, he said.

A team of 47 NDRF personnel was at the spot and the situation was brought under control by 3 pm, as firefighters and Noida Police officials, including senior officers, remained deployed at the site.

'An alert call was received on emergency 112 service of the police. People were immediately evacuated from the building,' a police spokesperson said.

Firefighters, who responded to the emergency, had diluted the ammonia gas which had got mixed in the air in and around the building, a Fire Department official said.

'We sprayed water in the air to neutralise the ammonia. Ammonia solution was also used on the condensers to check the leak. The main gas pipeline has been closed since,' the official said.

Exposure to high concentrations of ammonia, also used as a refrigerant gas, causes immediate burning of eyes, nose, throat and respiratory tract and can result in blindness, lung damage or death.