Prima facie it appeared that rupture in a pipeline carrying the gas to the factory resulted into the leakage, which has been stopped, according to a fire department official.
"Seven persons, including a woman, asphyxiated to death after ammonia gas leakage in a cold storage factory at Ranasan GIDC in Vijapur taluka here," police said.
The deceased are identified as Rahul Teja (20), Vihol Baldevsinh (35), Vihol Laxmansinh (40), Hirensinh Laxmansinh (40) and Daksha Naransinh (40)--all hailing from Pilvai village in Vijapur taluka---and Sanjay Parmar (22) of Vijapur and Shrelkumar Rathod (33) of Ranasan, police said.
Earlier, firemen gained entry into the unit after cutting the roof and razing the sidewall.
Three teams of fire brigade from Mansa, Mehsana and Vijapur, along with a team from ONGC, and police were involved in rescue operations.