The mother of an 18-year-old who was killed in a fire at an apartment building in Lawrence Heights on Monday night has died, Toronto Fire said.

The fire broke out at a Toronto Community Housing building in the area of Flemington and Allen roads at around 9:40 p.m.

Upon arrival at the scene, firefighters made a forcible entrance into a unit on the first floor of the three-storey apartment building.

A 47-year-old woman and her two teenage sons were rushed to hospital in critical condition after the fire broke out.

The 18-year-old son died of his injuries while in hospital on Tuesday.

Toronto Fire confirmed to CTV News Toronto on Friday that the mother had died as well, but could not confirm the cause of her death.

The 16-year-old son remains in hospital in critical condition.

The fire was extinguished at around 10 p.m. and the cause of the blaze remains under investigation.