SA train derailment under investigation

Services have resumed on a suburban Adelaide rail line after a train carrying about 20 passengers derailed and collided with a buffer.

The train slid off the tracks at the end of Grange railway station around 6.30pm on Tuesday and hit a bumper stop next to Military Rd.

Passengers and staff were uninjured and safely disembarked.

Services on the Grange line resumed on Wednesday after repairs were completed overnight.

Public Transport Authority executive director Scott White said the incident would be investigated to determine what caused the derailment.

"We don't know yet. There's lots of things that need to be looked at," he told ABC radio.

"Our safety systems worked as they were supposed to."

Transport Minister Tom Koutsantonis said the Office of the National Rail Safety Regulator was assisting the investigation.