A four-member probe body formed by Titas Gas Distribution and Transmission Company Ltd to investigate into the blast in Bhaluka of Mymensingh on the night of March 25 found that the blast did not occur from 'gas line leakage'.
Four final year students of Textile Engineering Department of Khulna University of Science and Technology (Kuet) were killed in the blast.
They deceased were Hafizur Rahman Hafiz, 24, Dipto Sarkar, 22, Shahin Mia, 22, and Towhidul Islam.
They were interns at Square Fashion in Mymensingh's Bhaluka upazila. They lived in a rented-flat in a newly constructed six-storey building in the upazila's Masterbari area.
The probe body led by Rana Akhter Haidari, general manger (Marketing, North) of Titas Gas Distribution and Transmission Company Ltd, submitted the report to its higher authorities on Tuesday, said Engineer Moshihur Rahman, deputy managing director (Mymensingh) of the company.
Quoting the probe report, Moshihur said the blast was not from gas line leakage but he could not specify the actual cause behind the accident. Now police could reveal it, he said.
Atiqul Islam, deputy manager (Bhaluka) of the company, lodged a case, accusing house owner Abdur Razzaq Dhali for illegal gas connection and his neighbour Abdul Gani, who assisted Dhali, said engineer Moshihur.
The gas connection at the building was illegal, the official said, adding that the house owner did not get any permission for gas connection and he did it on his own accord.
For alleged negligence of duty, Monjur Ahmed, the manager of Bhaluka office of the company was transferred on March 27, said the engineer.
The house owner took bail from the High Court on April 8, said Md Ashiqur Rahman, officer-in-charge of DB, Mymensingh.
Two separate probe bodies by police and district administration were formed to investigate the incident but the reports are yet to be submitted.