They said the nature of debris and causalities showed gas accumulated from anywhere might turn a closed room into a gas chamber at the basement of the blinding and a spark from any source might cause this huge explosion.

According to the bomb disposal unit, gas might accumulate for five possible reasons.

These are: gas might emit from unground water tank of the building; there was a septic tank between the two buildings and gas might emit from it; gas might amass from a disconnected line or methane gas might accumulate on the wall of the building; gas might gather from a leakage of sewerage pipeline, and finally gas might accumulate anyhow from the big generator of the building.

Speaking to Prothom Alo, CTTC’s bomb disposal unit additional deputy commissioner (ADC) Rahmat Ullah Chowdhury said gas anyhow accumulated in a closed room of the building and they primarily suspected a spark from an electric short circuit or anything else might cause the blast.

This is no sabotage, ADC Rahmat Ullah Chowdhury observed adding, no existence of improvised explosive device (IED) was found as well as no evidence of coloured or black smoke usually occurred from IED was found either.

Injury marks on dead bodies recovered from the blast site also showed the explosion may occur from accumulated gas. The nature of injuries on people undergoing treatment showed gas layer was 3-5 feet high and the explosion occurred from methane gas.

The blast at Queen Sanitary Market left at least 20 people dead and scores injured. Of the inured, 20 people are now under treatment at Dhaka Medical College Hospital.