Faults in gas connections of Titas Gas Transmission and Distribution Company Limited or negligence of City Corporation authorities during drain excavation in the area might have caused the blast in Moghbazar, as per the case statement filed by police over the Sunday's accident that left eight people dead and hundreds, including many pedestrians and commuters, injured.
In the case statement, the investigation team also said a leakage in the gas connection was the main reason behind the blast.
The findings echo the observation of the Department of Explosives that had detected the presence of hydrocarbon at a risky level at the site and traced leakage in Titas gas connection.
A cycle rickshaw van puller named Md Tamjid, who had unloaded products of Singer Electronics one hour before the blast, said he had smelled gas in the building.
However, Titas Managing Director Ali Iqbal Md Nurullah claimed on Tuesday that there was no gas connection of Titas in the building.
Ramna police filed a case over the explosion against unidentified people, alleging that the deaths had been caused by negligence.
The committee formed by the police headquarters ruled out any possibility of an act of sabotage after visiting the damaged building on Tuesday morning.
The chief of the committee, Asaduzzaman Mia, additional commissioner at Counter Terrorism Unit, said they visited the site with a gas detector and 12-13% methane gas was detected.
According to the case statement, the explosion may have been caused by the mismanagement of the building owner, old electric connections, faulty gas management, use of unauthorised gas and electrical materials from Sharma House and Bengal Meat or the unplanned drain construction of the Dhaka North.
When gas accumulated in a confined space and mixed with air, it makes an explosive agent that may have caused the destruction, one of the probe body members told TBS.
The chief explosive inspector of the Department of Explosives, Abul Kalam Azad said natural gas might have accumulated inside a closed room and sparked the blast from there.
Meanwhile, another body was recovered on Tuesday afternoon from the site, raising the death toll to eight.
The body of Harunur Rashid, 71, a security guard of the three-storey building, was recovered by fire service around 3.30pm, Fire Service Assistant Director Shahidul Islam Suman told TBS.
Firefighting officials said they recovered the body from debris beneath the stairs of the ground floor of the damaged building. The body was sent to Dhaka Medical College Hospital morgue for an autopsy.
Another security guard of the building remained missing since the blast on Sunday.
Opposite the Moghbazar branch of Aarong on Shaheed Sangbadik Selina Parvin Road, the three-storey building houses Shawrma House, Bengal Meat and Grand Confectionary on the ground floor and the warehouse of Singer Electronics on the first floor.