A six-year-old girl discovered her mother's lifeless body in a home in Brisbane's south after the child was unlocked from a bedroom and told by her father to call an ambulance, a neighbour says.

Emergency crews were called to a home on Waratah Drive in the Logan suburb of Crestmead just after 7am on Wednesday, where they found the dead woman.

Neighbours reported seeing a man "covered in blood" and crying as he was led by police from the house.

A police spokeswoman said she did not know how the 24-year-old woman died.