A woman and child have drowned in Melbourne's south-east after being swept into a waterway in Dandenong.

Police said a witness reported two people fell into Dandenong Creek, near Allan Street, about 3:45pm on Monday.

Authorities believe the woman went to the aid of the child, and also got into difficulty before being swept away.

Police searched the area and located the unconscious pair in the water, starting CPR.

However, the pair were unable to be revived and both the woman and child were declared dead at the scene.

The two people are yet to be identified and police will prepare a report for the coroner.

Anyone who witnessed the incident or has information has been urged to contact Crime Stoppers on 1800 333 000.

See Full Page