Police in Sydney's inner west are investigating what they believe may have been a murder-suicide after the bodies of a man and a young girl were recovered from the Parramatta River over the weekend.

Emergency services were called to Hen and Chicken Bay at Concord on Saturday morning after reports that a man had been seen floating in the water. Despite rescue efforts, he was pronounced dead at the scene. Witnesses had earlier observed him travelling in a small hired boat with a young child.

A large-scale search operation was immediately launched when the child could not be located. Marine rescue crews, police divers and aerial resources spent several hours searching the river before the girl's body was found later that afternoon.

Investigators now suspect the incident may have been a deliberate act. Police have reportedly recovered evidence from the man's residence, including a note and electronic data that are being examined as part of the investigation. Authorities are also reviewing communications sent before the incident occurred.

According to investigators, concerns about the welfare of both the man and child were raised by a friend on the day of the incident. Police are working to establish the full sequence of events and determine what led to the tragedy.

The child's mother has been notified and is assisting police with inquiries. Authorities confirmed she is not suspected of any wrongdoing. Support services are being provided to family members affected by the incident.

Senior police officers described the deaths as a devastating event for both the family and the wider community. Investigators are also examining whether domestic or family violence factors may have played any role in the circumstances leading up to the deaths.

A report will be prepared for the coroner as police continue gathering evidence and interviewing witnesses. Authorities have appealed for anyone with information about the movements of the man or child before the incident to contact investigators.