Victoria's roads authority has grounded more trucks from the Cootes fleet, with faulty brakes among defects found.
Six trucks were grounded on Sunday as authorities examined Cootes Transport's fleet of LPG vehicles.
The company voluntarily agreed on Friday to immediately ground its fuel and LPG fleets over safety concerns, only days after a third of its large NSW operation was ordered off the road when major defects were detected.
VicRoads inspected 23 vehicles at Cootes Dandenong site on Sunday, grounding six trucks, with another seven vehicles passing inspections only after being repaired on site.
Two vehicles required minor repairs, while eight passed inspection.
Faults found on Sunday included brakes, loose brackets, bolts and fixtures, oil and fluid leaks, shock absorbers and cracks in mounts.
VicRoads said in a statement 16 prime movers and nine trailers have been returned to the roads after inspections by VicRoads, NSW Road and Maritime Services or independent licensed road worthy testers.
The organisation said the defects are not as severe as those found in October last year.
Last October, VicRoads grounded Cootes prime movers and trailers for severe defects during a sweeping fleet review prompted by a fuel tanker explosion in Sydney that killed two people and involved a Cootes vehicle.
Cootes had advised VicRoads it had improved its maintenance regime "significantly" since the October audit.
VicRoads acting chief executive Peter Todd said on Saturday there is no need for Victorians to panic buy petrol.
"We've got some advice that there will be plenty of fuel in Melbourne and in Victoria," he told reporters on Saturday.
"People shouldn't panic, they don't need to rush out and buy."