Authorities suspect a fire that destroyed three businesses in southern Brisbane early this morning was deliberately lit.

A crime scene has been established at the Salisbury industrial complex.

Authorities had said four businesses were affected, but Fox Flags owner Darrell Lane later said it was three firms that had been destroyed.

"Between the three of us businesses, probably in the vicinity of 2 million bucks [in damage] I think," he said.

A worker at one of the businesses, Bill Harpur, told the ABC he believed a car was deliberately set alight at the back of the site.

The blaze broke out about 1:30am this morning in the building on Evans Road at Salisbury.

It took 11 fire crews to stop the blaze, which gutted four businesses where about 20 people work.

"It looks like a skip has been pushed up against the building and the car's been beside that and they've set fire to the car, which has subsequently set the skip alight, which has set the building alight," he said.

"It's a bit hard to put into words what you think. I mean, standing across the road from our livelihood and it's not just me, it's the other people who work there and the people in the business next door.

"You know, 20 or 30 people's lives have been affected by this ... it's a bit hard to describe. [I'm a] bit numb at the moment, really."

Mr Lane said he did not know whether his company would ever reopen.

"Ruined a number of lives and taken 30 years of my life from me and all the people who work for me, who I consider family, it's devastating," he said.

"I'm in my 60s - how do I replace 30 years?

"I do a lot for a lot of people. I even make QFRS flags. I make QPS flags, Queensland Police Service flags, so who's going to replace those?"

Maria Villalbagauto, who worked at one of the businesses destroyed by the blaze, does not know what will come next.

"It's a very sad moment. I can't understand how the people that did [it] don't think about the people who work there, because we're all out of a job," she said.

"The rest of the staff will be devastated. Especially my boss — he worked really hard for this and now it's all gone in flames.

"I hope I still have a job; I hope he [the boss] can rebuild it so we can all have a job."

Police investigate stolen vehicle set alight

The vehicle police believe was deliberately set alight at the back of the Salisbury site may have been stolen last week, Detective Senior Sergeant Tony Geary said.

Police were canvassing local businesses in the hope of obtaining CCTV footage.

"We believe the vehicle is a VW and we believe it may have been stolen from the West End area in the last week," he said.

"We're making attempts now to contact the owner of that vehicle to ascertain where and when it was actually stolen.

"Then we'll conduct investigations to establish whether or not it's been used in any other offences."

Detective Geary said he was unable to provide details of the colour or the registration.

He was also unable to provide information about the offender or offenders.

A stolen car linked to the fire that gutted a Salisbury industrial complex early this morning. ( ABC News )

"We'll have a look around the area.

"Hopefully some local businesses will have some CCTV and we can have a look and see if we can identify the persons responsible."

He appealed for anyone with information to come forward.

"If anyone was in the vicinity of Evans Road at 1:30am this morning and may have seen anyone in the area or a vehicle that was acting suspiciously, we ask them to contact crime stoppers," he said.

He estimated the damage as in excess of $5 million.

"As a matter of our investigations we'll interview employees and employers of the business premises just to establish what, if any, information they can provide to assist us with the investigation.

"The owners of these premises have lost trade and potentially lost their livelihoods for a period of time due to the nature of the offence."