Teams from the state CID and forensic department started their investigation into the explosion at an illegal firecracker factory in Egra area of West Bengal’s East Mednapore district on Wednesday, a senior officer said. Forensic experts started collecting samples from now collapsed house at Khadikul village which housed the illegal firecracker unit and its surroundings, he said. The CID officers will speak to witnesses as well as with family members of those killed in the blast, the officer said. A huge posse of local police have been deployed in village near the Odisha border.