Several people are stranded between the Cullen River Crossing and Edith River Bridge Crossing, as the Stuart Highway remains impassable due to flood waters.

Police at Adelaide River are advising motorists they can not travel further south than Pine Creek and police at Pine Creek have set up a road block to prevent people driving into the flood affected area.

"Authorities have also made contact with two families that have been forced to evacuate to their rooves as floodwater inundated their homes on Edith Farms Road." Said Commander David Proctor.

"Initial indications are they have plenty of food and water. A minor flood watch has also been declared for Gorge Road near Katherine, but the town is not expected to be threatened by flooding at this stage," Commander Proctor said.

"Police have now also reached the scene of a freight train derailment north of Edith Falls River Crossing.

The driver and co-driver are being medically assessed after having walked to the Stuart Highway. The ATSB has been notified of the crash and will take carriage of the investigation."

The pair will be taken to the Katherine District Hospital.

Police would like to reinforce to motorists that the Stuart Highway is closed to the South from Pine Creek and they should not attempt to travel until advised that the Highway is reopened.