As per routine, the couple used to return by 12 noon. During their absence, their elder daughter Kalpana, 8, used to look after her younger sister Retu, 5, and brother Chetan, 3.
On Thursday, the couple left for work, locking behind their single-room house.
According to the neighbours, they noticed smoke emitting from the house at 9 am, they broke open door and controlled the fire, but by that time the children had died of suffocation.
The entire neighbours who took part in the rescue operation also informed the parents at their work-place in Garden area.
Police, after questioning the parents, said that they suspected that smouldering “oil lamp” fell on bed sheets which caught fire.
Police learnt about the incident at 10:30 am. Police shifted the bodies to Civil Hospital for post-mortem.
The family was living in the house for the past one year; the couple was employed in an apartment complex in Garden West.
It is the second such incident in a fortnight. On April 29, eight members of a family died in an apartment fire in Gulshan-i-Iqbal. The fire had broken out due to an electric short-circuit.