Brisbane police linked the fatal stabbing of a schoolgirl to the death of her mother, who committed bridge suicide on Wednesday.

Scientific and scene of crime officers searched the family house in Paddington to establish the connection between the two deaths.

The mother jumped to her death off Story Bridge in Brisbane during the morning rush hour. News.com.au reports that the woman parked her vehicle on the bridge's left lane at about 6:45 a.m., climbed over the railing and jumped. Several motorists witnessed her suicide try.

Reports said the woman left a boy, likely her son, inside the abandoned car. The child was brought to a hospital and is believed not suffering from any injuries.

A few minutes after the bridge suicide, police got a call at about 7 a.m. about the body of a teenage girl with stab wounds. The dead girl was the daughter of the woman who jumped off the bridge, Detective Inspector Tony Duncan confirmed.

There was no apparent witness to the schoolgirl's stabbing, Mr Duncan said. He ruled out suicide as the cause of the girl's demise.