The accident took place in Chandradigholia area of the upazila before Saturday dawn.
The cropses of Rabeya Begum, 35, and her son Rifat were sent to the district hospital morgue for autopsy. She is wife of Hasibur Rahman Hasib, from Haridaspur village in the upazila,
Hasib was also injured in the accident, who was taken to Dhaka in a critical condition.
Sadar police station OC Selim Reza said a pick up van carrying the three collided head-on with a truck because of dense fog while they were on the way to home from Dhaka.
Rabeya and her child died instantly while the driver fled the spot soon after the accident.