Mystery over seriously injured SA man

Police have released an image of an Adelaide man in a bid to find out how he sustained serious head injuries which have left him in an induced coma.

The 39-year-old from Davoren Park was injured when he arrived on foot at a nearby address late on Tuesday night.

Police say the householders called an ambulance for the disorientated man who was bleeding from a head injury.

He'd suffered a fractured skull and bleeding on the brain, and is now in intensive care in an induced coma at the Royal Adelaide Hospital.

Police say the IT worker left his workplace in Adelaide and possibly caught the 8.50pm train which arrived at Broadmeadows Railway Station about 9.30pm.

Detective Inspector Peter Dunstone said on Friday the man's injuries were consistent with him suffering a serious assault but police were not yet able to confirm what happened.

"Police are seeking assistance from anyone who may have seen this man, who is of Asian appearance, prior to his arrival at the address," he said.