Update after young man's body found on Barrpowell St, Welland in Adelaide

Police are investigating the discovery of a skateboard, tyre tracks and a pool of blood at the scene where a young man's body was found on a quiet street in an Adelaide inner suburb.

Emergency services were called about 1.30am on Wednesday to a street in Welland - a chiefly light industrial area in the city's inner northwest - and found a 21-year-old man unresponsive on Barrpowell Street.

South Australian Police Detective Superintendent Des Bray said the young man was murdered and the police suspect the victim and offender knew one another.

'This young man, we believe, arranged to meet somebody, in this street, at 1.30am. On that basis, we do not believe this death was committed by some random stranger,' he said just before midday.

'I am confident, given that the majority of murders are solved in this state, I have no doubt we will get to the bottom of this. And we've got a large number of detectives and uniformed people working across Adelaide at the moment.'

Detective Superintendent Bray said witnesses who heard a disturbance tried to render assistance to the man, but could not revive him.

'This young fellow has come to the street, obviously to meet somebody, as to how it unfolded or why, we can't say,' he said.

'He died a needless and senseless death.'

'When we get to the bottom of this, it will be for some trivial reason.'

Police are calling on security guards from surrounding properties or anyone in the area between 1am and 2am to come forward to the police.

'We do know this lad walked into the area, so he probably lived somewhere not far from here,' he said.

A puddle of blood can be seen within a couple of metres of a skateboard and multiple tyre marks in the cul-de-sac.