Nguyen Thi Ngoc Thom, a 26-year-old Phu My District resident, was transporting her mother-in-law and two children to a medical check-up on Friday when the accident happened.
Four-year-old Yen sat on the front, while the mother-in-law and Thom's 1-year-old son sat in the back.
On the way, Thom stopped by her father's house, where she asked her father to look after Yen. But Yen grabbed onto the handle of the motorbike and inadvertently accelerated the vehicle, causing it to ram into a fence. The impact killed Thom's mother-in-law and her two children, while Thom herself was also injured.
An investigation is ongoing, according to Phan Huu Duy, standing deputy chairman of Phu My District.