The three criminals, whose weight machine exploded at Pallabi Police Station today after their arrest, are not members of a militant group, said Krishna Pada Roy, additional commissioner (crime) of Dhaka Metropolitan Police.

They are members of a criminal group, the police official replied to a query while briefing after visiting the police station today.

A team of Pallabi police during a drive yesterday arrested the three criminals along with firearms, bullets and some other things including the weight machine.

Four police personnel and a staff of the police station were injured when the weight machine exploded in the morning there, police said.

During the briefing, Krishna Pada Roy, said interrogation of the three arrestees is underway.

Primarily, police came to know that they had a plan to commit a crime in the area.

Replying to a query, he said there was no connection between the blast and security alert issued by Police Headquarters.

An expert team of bomb disposal unit have already deactivated two more objects at the police station, he informed.

Bomb disposal squad of DMP's Counter Terrorism and Transnational Crime Unit collected the remains of the exploded device for investigation.

"Militant groups do not use these kind of explosives. Usually, we see criminal groups use such explosives," Additional Deputy Commissioner Rahmatullah Chowdhury, also in-charge of the squad, told The Daily Star.