According to the Hull Daily Mail, firefighters were called to the Space Projects Ltd site off Carlton Street at around 3.45pm where they discovered huge flames and plumes of thick smoke.
They battled the fire for around an hour before bringing it under control. The site remained cordoned off while the area was dampened down. There are no reports of any injuries.
Humberside Fire and Rescue spokesman Rick Phillips said: “The fire was started by a spark from a grinder being used by a worker.
“There was no one on the buildings at the time but we had to lead some workers in the yard to safety.”
The Responsible Person can face an unlimited fine or up to two years in prison if the assessment is found to have been carried out to an insufficient extent.