The explosion which injured three members of a family in Barishal's Bakerganj upazila on Monday morning was caused by a locally made improvised explosive device (IED), said police.

"Based on the preliminary examination, the bomb disposal unit confirmed that it was an improvised explosive device. It was locally made," Barishal Superintendent of Police AZM Mostafizur Rahman said.

A four-member bomb disposal unit searched the entire area and collected several samples from the scene.

The explosion occurred around 6:30am in Dudhal Mou village under Bhorpasha union. The injured are Hanufa Begum, 55, her daughter Iti, 19, and Hanufa's grandson Fahim, 14.

According to relatives, Hanufa and Iti were taking Fahim to his coaching class.

Jamal Hawlader, a family member, said there were several sandbags in front of the house.

“As they stumbled near the sandbags, a bag that had apparently been left there exploded,” he added.

The three were taken to Bakerganj Upazila Health Complex, where they received primary treatment before being transferred to Sher-e-Bangla Medical College Hospital in Barishal.

Later, doctors referred them to Dhaka for advanced treatment, and they were shifted by ambulance.

Police initially said they could not determine the cause of the explosion.

The area had been cordoned off following the incident.