Police seized bomb-making materials in the wake of the explosion from the office of Manabmukti Samajkalyan Sangstha that police said was working as an undercover recruiting agency.

Police took injured Kazi Mohammadullah Shohag, 22, a staff of the NGO, into their custody after first aid for interrogation and critically injured Khorshed Alam Ripon, 24, who claimed himself to be a taxicab driver, is undergoing treatment at the Orthopaedic Hospital.

Witnesses said the bomb exploded with a big bang at the Sangstha on the first floor of the market at 2:05pm and blew off the glass door and parts of a shutter of the office.

Shopkeepers of the market rushed to the scene and saw a young man trying to crawl out of the office covered with a thick layer of smoke.

He suffered critical injuries to his face, chest, right hand and legs.

The shopkeepers rushed the injured pair to Dhaka Medical College Hospital (DMCH) from where Ripon was shifted to the Orthopaedic Hospital in the evening as his condition deteriorated.

"We conducted a thorough search and found bomb-building materials including gunpowder, pieces of stone, empty bottles and three rolls of tape," Officer-in-Charge of Ramna Police Station Mahbubur Rahman told The Daily Star.

The staff of nearby shops said the NGO, owned by one Waliur Rahman of Azimpur, was taking money from people in the name of giving them job in the NGO for the last two and a half years.

"It is a fake recruiting agency," the Ramna OC said.

Police did not find Waliur at his home.

Mahbubur alleged Ripon was a member of the Gopal-Babul gang in Farmgate and lived in Kathalbagan before going underground.

Denying his role in bomb-building, Ripon said he was standing outside the Sangstha office when the bomb went off.

But Shohag, who also denied the charge, said they were sitting at the office when three young men passed by and the bomb exploded.

He said the NGO ran several projects on mass education, poultry and tailoring.

Hospital sources said Ripon's injuries suggest the bomb might have exploded in his hand or at a close distance.

"They are professional bomb-builders," the Ramna OC alleged. "I think they worked as bomb suppliers and hired the office to carry on the crime under the cover of an NGO."

On the same day, A seven-year-old girl suffered bomb injuries in Demra, police said.

Yasmin was playing with some others near their house at Demra Bahserpool at 5:00pm when a boy handed over a container to a girl.

As the children began playing with container, it went off and Yasmin suffered splinter injuries.