Four members of a family, including a child, sustained burn injuries after a mobile phone charger reportedly exploded and triggered a fire at their residence in Narayanganj's Sonargaon upazila early today.

The fire broke out around 4:30am inside their third-floor room in Patatta of Kanchpur union, said Sonargaon Police Station Officer-in-Charge Rashedul Hasan Khan.

The injured — garment worker Md Alaudddin, 35, his two daughters – Shifa Akter, 14, and Simla Akhter, 4, and his mother Jorina Begum, 65 — were admitted to National Institute of Burn and Plastic Surgery in Dhaka in the morning.

Dr Shawon Bin Rahman, resident surgeon of the institute, said Alaudddin suffered 40 percent burns, while Simla 30 percent, Jorina 20 percent, and Shifa 12.

The OC added, "Primarily, we suspect the fire originated from a charger explosion while the phone was plugged in."

Abdullah Al Arifin, deputy assistant director of Narayanganj Fire Service and Civil Defence, said they were not notified immediately after the incident.

"Later, a team inspected the building and found that gas had likely leaked from a Titas Gas line connected to a small kitchen beside the room," he added, suggesting the accumulated gas may have intensified the fire.

Alaudddin's sister Salma Akter said hearing a loud sound while coming out of the washroom, he had rushed inside to find the room engulfed in flames and his mother and children burning.

Alaudddin sustained burns while trying to extinguish the fire, she added.

Hearing screams, neighbours rescued them and rushed them to the hospital.