Firefighters battled the flames at Boarhunt in Fort Wallington Industrial Estate, in Military Road, Fareham, from 8.49pm.
Now police have said officers and the fire service are investigating the incident as a possible arson.
Two forklift trucks, a lorry and 15 cars were destroyed in the blaze.
A Hampshire police spokesman said: 'A number of vehicles were damaged.
'˜We are working with our colleagues from Hampshire Fire and Rescue Service to establish the cause of the fire which is being treated as suspicious.'
Call police on 101 quotingÂ 44180288212.