A 72-year-old man has been found dead in a burnt-out home in Brisbane's south, after a neighbour managed to help the other occupant escape.

Emergency services were called to a Gregory Street address in Acacia Ridge about 10pm on Thursday to find the building already engulfed in flames.

The man and a 71-year-old woman had both been home at the time.

However, their neighbour, a 56-year-old man, was able to help the woman out of the house. Both were transported to hospital with minor injuries.

The 72-year-old man was later found dead in the home.

Police have declared a crime scene while investigators work to determine what caused the blaze.

Anyone with information should contact Policelink on 13 14 44 or Crime Stoppers on 1800 333 000.