The deceased was identified as Ferdousi Begum, 30, wife of Tofazzal Hossain of Baburail area in the district town.
Relatives said five of the family members were injured as the wall of the building collapsed following the septic tank blast while they were sleeping early morning of March 27.
Later, the injured were taken to Narayanganj General Hospital where doctor declared a child, Ahmed, aged eight months, dead.
The rest were sent to Dhaka Medical College Hospital (DMCH) where the mother Ferdousi Begum succumbed to her injuries while undergoing treatment this morning.
At present, Tofazzal Hossain, 50, his son Mohammad Hossain, 9, and daughter Halima Begum, 11, are undergoing treatment at the DMCH, sources added.
Abu Taher Hossain, a resident of the area, said there were some leakages in some points of the gas line in the locality.
Although the inmates informed the concerned authority several times, they didn’t pay heed in this connection.