Vauxhalls, Renaults, a Mini and an Audi were among 21 vehicles burnt out after the blaze in a section of the site, which contains 2000 cars run by Lowcostairportparking.com
Firefighters responded to reports 10 cars were alight at 1.16am yesterday at the Lochend Industrial Estate in Newbridge. However, they were powerless to prevent the blaze spreading from vehicle to vehicle.
Two fire appliances and 10 firefighters were unable to put out the flames with high pressure hose reels until 4.22am by which time the damage had been done. Nobody was hurt in the incident.
One onlooker said: "There was every kind of car alight and by the end you couldn't tell the difference between an Audi and a Vauxhall. They were all burned to a crisp.
"Most of the owners will be on holiday. They will be devastated to come back to this.
"All the bonnets were blown up.
"It's just amazing that more cars weren't destroyed as the car park was full and they were tightly packed together."
A Scottish Fire and Rescue Service Investigation Unit is attempting to determine the cause. Police Scotland may also become involved depending on the outcome.
The car parking firm claims on its website that business travellers and holidaymakers alike can have "peace of mind" by knowing their vehicle will be left safe and secure.
A spokeswoman for the car parking firm said they were helping investigators, but added: "Until we know what has happened we can't say any more."