Police have filed a case over deaths due to negligence against unidentified persons in connection with Tuesday's deadly blast at a building in the capital's Gulistan area.

Palash Saha, sub-inspector of Bangshal Police Station, filed the case last night for deaths due to negligence, Mujibur Rahman, officer-in-charge, told The Daily Star today.

On Wednesday, police filed an unnatural death case over the same incident.

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Gulistan blast: Fire safety professionals gather on site to raise awareness

Yesterday, detectives arrested three people over the blast, which has so far claimed 22 lives. They are building owners -- Wahidur Rahman and his brother Matiur Rahman -- and a shop owner named Motaleb Mintu.

According to police, the two brothers were arrested as the building was built without following the relevant laws and rules.

Fire officials said the explosion took place around 4:45pm on Tuesday.

The cause is still not known but officials suspect that accumulated gas might have led to the explosion.