A woman is dead and a three-year-old child is in hospital in critical condition after a fire broke out Saturday night inside a low-rise apartment building in the city's west end.

The woman, who is believed to be in her late 30s, was pronounced dead at the scene. The young girl was found without vital signs but she is fighting for her life at the Hospital for Sick Children.

It is not clear how the two victims are related.

A neighbour called emergency crews to the five-storey Rosemount Avenue apartment, located in the Weston Road and Lawrence Avenue area, at around 11:40 p.m.

Heavy smoke and flames were seen pouring out of a fifth-floor unit.

The Fire Marshal's Office is investigating what caused the blaze. Authorities say damages to the building are estimated to be around $100,000.

Toronto Fire Chief Bill Stewart says he wants to see changes that will ensure all residential units are equipped with working smoke detectors.