Bathinda, Sept. 15 -- Four days after twin blasts rocked a house at Bathinda's Jeeda village, leaving a father-son duo severely injured, the bomb disposal squad is facing an uphill task in removing residues of the unidentified explosive materials from the site. As per the police authorities, at least two blasts took place on Sunday when the experts and robots were cleaning up the explosive residue from the room where the blasts took place on September 10. A 19-year-old radicalised law student, Gurpreet Singh, was booked on Thursday for assembling high-intensity explosives. Police sources said a yellow-coloured powder was found after the explosion and it is suspected to be picric, a highly explosive chemical compound. Police sources said that photos of the picric acid were found in Gurpreet's phone and it is suspected that he had sourced several hazardous materials online. Investigators suspect that a cocktail of chemicals triggered the explosions in which Gurpreet and his father Jagtar Singh sustained injuries. Senior superintendent of police (SSP) Amneet Kondal said that no one suffered injuries when two small blasts occurred during the cleanup of the blast site on Sunday. She said teams were expected to take another day before the house is declared free from the explosive residue. The SSP said that after post-hand amputation surgery, Gurpreet is still at the All India Institute of Medical Sciences (AIIMS), Bathinda, and he has yet to be formally arrested. "Gurpreet has been declared unfit by the doctors and we will arrest him for questioning after his medical condition improves," she said. She said Gurpreet's father Jagtar has been referred to Guru Gobind Singh Medical College, Faridkot, as the victim has developed serious injuries in eyes. Police had earlier confirmed that Gurpreet was found radicalised by the Islamic extremists and his digital activities showed him following the Pakistan-based terrorist Azhar Masood. SSP Kondal said a detailed report of forensic experts is yet to be received, if the picric acid was in the possession of Gurpreet. "Prima facie Gurpreet possessed chemicals, including ammonium nitrate, ammonium sulphate, lead nitrate and phosphorus pentoxide, when he mishandled it," the SSP said....