Residents in Hexthorpe, Balby and Warmsworth have all reported heavy emergency services activity, with police, fire and ambulance crews all dispatched to the scene near to Hexthorpe Flatts park.
It is understood officers have been spotted in a number of locations along the river.
There have been unconfimed reports that a man has been rescued from the waters.
Eyewitness Mark Laidler said: “They were parked on Guest Lane at Warmsworth.
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"There is a metal barrier which was closed that leads down to a track to Warmsworth Cemetry and riverside access too.
“The barrier was later opened - it was a good walk to where the scene was.”
Residents also reported vehicles in the St Peter’s Road and Smith Square areas of Balby.
Others said they had seen vehicles ‘flying down’ Greenfield Lane, with sirens and blue lights blazing.
A post on the Balby and Hexthorpe Community Engagement Facebook page said: “Following reports of a male who has been seen in the River Don, police, fire and ambulance was called to the scene and the male has been rescued.”
The area near to Hexthorpe Flatts is popular with open water swimmers in hot weather, although there have been repeated warnings by emergency services to stay out of the river which is considered deep and dangerous.
We have contacted both South Yorkshire Police and South Yorkshire Fire and Rescue for details and confirmation.