Addressing a press conference here, party general secretary, member core committee Surjit Singh Rakhra and MP Prem Singh Chandumajra demanded that the Punjab government handover the probe to the CBI for a fair and independent inquiry.
Chandumjara said party had formed a panel of three lawyers who would submit their report into the issue within a week's time.
On June 1, the Punjab police claimed to have recovered explosive materials, including a pressure cooker bomb and some pipe bombs and several country-made pistols, here from a house at Darshan Nagar here.
While Harpreet was arrested by the police on the Patiala- Rajpura Road here, Rajatvir allegedly committed suicide by shooting himself in the house at Darshan Nagar.
The mother of an accused, Kiranjit Kaur, on the night of June 2, also ended her life by hanging herself at her house.