A freight train has derailed north of Adelaide, with several carriages coming off the track and at least one large container toppling onto the ground.

No injuries have been reported, according to police, but drivers have been asked to avoid the area because the train is blocking a major road and also holding up other rail services.

ABC Radio Adelaide listener Jennifer Edwards told Peter Goers, the host of the Evenings program, several carriages out of "about 20 or 30" appeared to have come off the track.

"They lost one whole container. That's a bit further back on the ground. It tilted off completely," she said.

"There's a slight bend a little bit further back where it actually probably happened and you can see where the track there is really crooked now.

"There was sort of an odd noise, as you can imagine. It sparked a fire a little bit further down, a grass fire, I imagine with the sparks."

The line connects Adelaide with Port Augusta and other parts of Australia and is a major freight route, as well as being used by the popular Ghan tourist service to Darwin.

In a statement, the Australian Rail Track Corporation (ARTC) said the derailment occurred at about 6:10pm between Bolivar and Two Wells.

"Three carriages in the middle of the train have derailed, emergency services have attended the site and there are no injuries," a spokesperson said.

"Services are being impacted and ARTC is working with customers to minimise service disruption.

"Safety investigators are now making their way to the site and ARTC will release more information when it becomes available."

Police said Gawler Road was currently closed between Drew Street and Donaldson Road.

"Diversions are in place but please avoid the area if you can," they said.