Families of the victims have blamed the Gurdaspur district administration for failing to shut down the "illegal" unit despite repeated pleas.
The two people killed and one injured in a blast in Punjab's border district of Tarn Taran were trying to make a bomb in a bottle, Punjab Chief Minister CApt Amarinder Singh said on Friday.
"The three people were digging a pit during night and were trying to make a bomb in a bottle with a mixture of some chemicals that exploded. Two died in this incident and one had injuries in his eyes," Singh said in Batala in Gurdaspur district.
"We will find out who were making these bombs, how were they being made and for whom these bombs were being made. It will be known," the chief minister said.
A specialised post-blast investigation team of the National Security Guards visited the explosion site on Friday, a day after a team of the National Investigating Agency visited there.
The blast took place on Wednesday night in an agricultural field near Kaler village.
The deceased were identified as Harpreet Singh, 19, of Bachre village, Bikram Singh, 22, of Kaddgill village. The injured was identified as Gurjant Singh, 27, who is being treated at a hospital.
On Thursday evening, DGP Dinkar Gupta said police cannot rule out terror angle in the blast at this stage.
Investigation agencies have found two pits in the agricultural field and were examining the call details and scanning the bank accounts of the trio.
There were reports that a few suspects have been rounded and their links with those dead in the blast or with radical organisations are being investigated, though there was no official confirmation.