Dhaka, Mar 9 (IANS): The death toll from the powerful explosion two days back at a commercial building in Bangladesh's capital Dhaka has reached 21 and is expected to rise, officials said on Thursday.

Rescue workers recovered the body of another victim from the five-storey commercial building in old Dhaka's Siddikbazar area on Thursday morning.

"With this, the death toll in the explosion rose to 21," Assistant Director of Fire Service Aktaruzzaman told journalists, adding that the death toll may rise further as 30 more critically-injured patients are undergoing treatment at different hospitals.

Fire officials said the explosion took place around 4:45 p.m. local time on Tuesday. The cause behind the huge blast is still not known, but officials suspect that accumulated gas might be a likely cause, Xinhua news agency reported.

Detective Branch of Bangladesh Police on Thursday detained three people, including the two owners of the five-floor building, Additional Deputy Commissioner (Media) of Dhaka Metropolitan Police KN Roy Niyoti told journalists.

"We're inquiring to know whose negligence caused this incident," he said and added they want to know why there were shops set up in the basement flouting regulations.