Man shot dead at Melb factory

A man gunned down at a Melbourne factory complex may have known his killer, police believe.

They found the man dead at an industrial estate at Campbellfield, with a gunshot wound to his upper body, after reports of loud bangs just after 6am on Thursday.

Detective Senior Sergeant Shane O'Connell does not think the victim, who has yet to be formally identified, worked at any of the businesses in the industrial block, which contains storage areas and small factories.

There were a number of people in the factories at the time, and they have been interviewed.

"The victim was an associate or friend of a number of people that were inside one of the factories," Det Sen Sgt O'Connell told reporters.

"There were some occupants in a very close factory, they were just socialising in that factory."

Police don't know what the man, believed to be in his 30s, was doing there.

But there was a suggestion the victim may have known the shooter.

"We're always concerned when incidents such as this happen," Det Sen Sgt O'Connell said.

"The information I have to hand at this stage is that there may be some relationship between both parties."

A police helicopter was hunting for the shooter on Thursday as forensic detectives searched the site.

Many workers were unable to enter their factories because much of the street was cordoned off.

One worker, who did not wish to be named, said there had been bikie activity on the street in the past.

"It was packed with motorcycles here, they have been here in numbers," he told AAP.

"We know the area is a bit rough here, we've had cars smashed into a pole here, they do burnouts."

But Joe Papley, an operations manager at one factory, said he wasn't too concerned about the incident, which was not common in the area.

"We haven't seen the street closed off like that before," Mr Papley said.

Det Snr Sgt O'Connell said at this stage there was no reason to believe drugs or bikies were involved and no evidence of organised crime.

Police haven't found the gun.