The Rapid Action Battalion (RAB) is suspecting that accumulated gas inside the basement may have caused Tuesday's (7 March) explosion in the Gulistan building that killed at least 18 and injured over 120 people.

Major Mashiur of the elite force's bomb-disposal unit, speaking with The Business Standard on Wednesday (8 March), said, "We, following preliminary probe, have found that the explosion originated from the basement of the building.

"Accumulated gas, from the building's sewerage or from the supply line of Titas, may have caused the blast."

"We have ruled out the possibility of an AC unit causing the explosion," the RAB official added.

"Also, to determine the exact cause of the incident, we are trying to recover the CCTV footage of a nearby shop," Major Mahsiur said.  

However, Titas Gas Director (Operation) Md Salim Mia, while addressing the press at the spot of the incident, said, "We didn't find any evidence of a gas leak in our supply lines.

"If that was the case, there would have been a massive fire in the building."

Meanwhile, Rajdhani Unnayan Kartripakkha (Rajuk) Director (Zone-5) Hafizul Islam, when asked about the legality of the establishment, said, "We are still searching for the documents related to the building.

"Only then will be able to say if it was built maintaining all the rules, regulations and codes."

Earlier on Sunday (5 March), three persons were killed and dozens were injured when a blast rocked the capital's Science Lab area.

CTTC's Bomb Disposal Unit confirmed that the blast happened due to accumulated methane gas. It was earlier suspected that the source of the explosion was either an AC unit or a gas cylinder.

The tragic incident occured a day after a blast in an oxygen plant in Chattogram's Sitakundu that claimed six lives.