An explosion of an ammonia tank pipeline at a dairy and ice cream production and storage plant resulted in one death and three injuries, local emergency services said Thursday.

The explosion took place at a plant owned by Binggrae Co. at around 1:05 p.m. that caused at least 1.5 tons of ammonia be released into the environment.

"Emergency efforts to contain the explosion and the subsequent leak of the chemical compound by the fire department and the military produced limited results," one official at the site located just east of Seoul said.

Rescue workers said a 55-year-old worker identified by his family name of Do was crushed to death when the explosion caused a building to collapse. He was found five hours after the explosion took place, with the search being delayed by smoke and concerns of secondary explosions.

Three other workers near the tank have been evacuated to a hospital. Some suffered broken limbs although doctors claimed the injuries were not life threatening. Ammonia requires considerable attention and can affect eyes and respiratory systems, yet it is not fatal to humans in most cases. It is used as a refrigerant for ice cream and other food products.

Besides those at the plant, four nearby residents living at an apartment complex have been evacuated to a hospital after experiencing physical discomfort.

The company said that a nearby liquefied nitrogen tank was not affected and the ammonia gas leak was stopped at 1:25 p.m.

Emergency workers are carrying out cleanup efforts, with investigators trying to determine why the tank exploded. Initially officials said the old pipes may be responsible.

"We are checking if workers and managers followed safety guidelines," one official at the site said.

The plant opened in 1979 covers 30,446 square meters, with most of the space being used as cold storage facility. (Yonhap)