A fire erupted at a residence on Merritt Street in Harristown, Toowoomba, around 12:30 am.

Upon the arrival of emergency services, they found the house completely consumed by flames.

The fire has now been put out.

Police said six people escaped the home, including a 34-year-old man, a 36-year-old woman, and four children.

The woman, and two of the children are in hospital with critical injuries.

The man is also in hospital with serious injuries.

A fifth child who was living at the home remains unaccounted for.

Investigations are underway to determine the cause of the fire, and anybody with information is urged to contact Crime Stoppers on 1800 333 000.