The mother of the three-day-old baby, who died in a collision between a bus and an ambulance in Taraganj upazila of Rangpur, has succumed to her injuries from the crash.
Moslema Begum, 30, died while undergoing treatment at Rangpur Medical College and Hospital on Sunday evening, Md Farhaduzzaman, the hospital's emergency department doctor told Bangla Tribune.
With this, the death toll in the accident rises to four.
Sheikh Mohammad Mahabub Morshed, officer-in-charge (OC) of Taraganj Highway police station, said a case was filed in this connection on Sunday.
According to police and family sources of the deceased, Moslema gave birth to her son at Nilphamari Sadar Hospital three days ago.
Earlier on Sunday, three people, including the baby, were killed and two others sustained injuries in a collision between a bus and an ambulance in Rangpur.
According to the police, the baby was unwell and was being taken to Rangpur Medical College Hospital for treatment.
A Panchagarh-bound bus coming from the opposite direction rammed into the ambulance at around 9am, leaving five on the second vehicle seriously injured.
Police and Fire Service rushed to the spot upon receiving the information and took them to Rangpur Medical College Hospital, where the doctor on duty pronounced three of them dead.