Three members of one family were burned in an explosion in Dudhalmou village of Bharpasha Union in Bakerganj, Barishal, on the morning of 3 August.
The explosion occurred at about 6am near the home of শাহ Alam Hawlader.
The injured were identified as Hanufa Begum, Shah Alam Hawlader’s wife; their daughter, Eti; and their grandson, Fahim.
They were first taken to Bakerganj উপজেলা Health Complex and later referred to Sher-e-Bangla Medical College Hospital in Barishal for further treatment.
Jamal Hawlader, a son of Hanufa Begum, said a bomb-like object hidden inside a sack of sand beside the house exploded.
He said the three people caught fire and entered the nearby Tulatala River in an effort to extinguish the flames.
Jamal Hawlader said the family did not know how the suspected object came to be there.
Bakerganj police inspected the scene after the incident.
Police also cordoned off the area and collected evidence, officials said.
Officer-in-Charge Adil Hossain said investigators had not yet determined what type of explosive material, if any, was involved or who may be connected to the incident.
The cause of the explosion, the source of the material and any responsibility remain unknown while the investigation continues.