The blaze broke out at Allens (Stourbridge) Transport Ltd site in Old Wharf Road, near Stourbridge Canal, at around 4.30am.
Fire crews from Stourbridge and Brierley Hill were sent to the scene where they found the flatbed lorries and storage garage alight in a gated yard at the front of the site.
They used one main jet and breathing apparatus to tackle the blaze and the fire was extinguished at around 6.10am.
A crew from Stourbridge Fire Station returned to the site at 8.30am with officers from the Environment Agency.
It followed concerns that diesel from the lorries could have leaked into the nearby canal.
West Midlands Fire Service confirmed an investigation into the cause of the fire was under way.
Workers at the firm declined to comment following the blaze.
Meanwhile a crash between two cars caused rush hour delays on the M6 today.
It happened northbound between junction 10 Walsall and 10A for the M54
At around 7.30am one lane was closed and traffic was queuing from junction 8 of the m5.