Firemen who raced to the scene were relieved to learn that the cylinders were empty.

The lorry had collided with a van, which crashed and landed on its side during the 11am incident that caused a massive jam on the highway.

Lorry driver Yusoff Abdullah said he was transporting the cylinders to Westport in Klang to be refilled when another lorry cut into his lane.

'I slammed the brakes but the lorry was too heavy, causing it to skid. I lost control of the vehicle and crashed into a van,' he said, adding that the incident caused several cylinders to fall, roll and land onto the roof of a workshop situated below the highway. Fortunately, the two workers in the shop were not injured.

The van driver suffered minor injuries and was treated at Kuala Lumpur Hospital.