If a co owns a veh and is self insured and then hires a driver for that vehicle from another co and the driver has an accident on the vehicle owners property which co would be responsible for damage?

A company owns a truck that is used to move semi-trailers and this company is self insured has leased a driver from another company and the driver has an accident on the truck owners property that involves only the truck who would be responsible for the damages. The company who owns the truck and their insurance or the company who leased the driver ?