The explosion that killed seven people at a building in Chattogram city took place when an inmate was lighting candle by match at a room on the ground floor.

“The explosion occurred this morning when my aunty Sandha lit match at the room for Puja purpose on the ground floor of the building,” said Arpita Debnath, 16, who sustained injuries in the blast.

Arpita’s parents -- Kajol Dah and his wife Monibala Nath -- recently went to their village home to celebrate puja keeping Arpita and their son Arnab Debnath, 8, under custody of Sandha.

“A wall of the ground floor was blown off during the explosion,” Arpita told our Chattogram correspondent.

Arpita’s brother Arnab, however, escaped the incident as he was out of the home at that time.

Arpita, who suffered 30 per cent burns in the explosion, was immediately referred to Dhaka from Chattogram Medical College Hospital as her condition deteriorated, said Mozaffar Hossain, a doctor of the CMCH burn unit.

Sandha, who also sustained injuries in the accident, is now undergoing treatment at the CMCH, the doctor said.

Purna Chandra Mutsuddi, deputy assistant director of Chattogram Fire Service and Civil Defence, said the seven people killed in the blast were believed to be pedestrians while eight of the 10 injured are also passerby.

Abdul Hamid, driver of a CNG-run auto-rickshaw, told the correspondent that he suffered injuries in his head, chest and waist as some brick chips of the collapsed building hit him when he was taking tea at a shop near the building.

Three rickshaw passengers were also sustained injuries during the blast at the same place.

The explosion occurred on the ground floor of a five-storey building on Brickfield Road around 8:30am, Mohammad Mohsin, officer-in-charge (OC) of Kotwali Police Station, told The Daily Star.

Fire service official Purna Chandra Mutsuddi said a major portion of the ground floor was blown off in the explosion.