A worker was critically injured in an explosion yesterday when he tested a container's contents with a lighter. Two other men were injured in the blast at a goods examination centre in Lok Ma Chau. The container, described as being packed with bags of polystyrene, was taken to the plant in Ho Sheung Heung Road, Kwu Tung, for inspection. The 24 tonnes of granulated material, which arrived from Europe for shipment to the mainland, was to be used for making transparent plastic products. The blast happened at about 11.30am when the container was opened and one of the two examiners, Yip King-leung, 48, used a lighter to burn a sample of the material on a concrete platform. His colleague and the truck driver were also on the platform. 'The victims told us that they burned the substance and smelt it in the test,' said police Chief Inspector Siu Heung-wing. A fire officer suspected the sealed container had filled with gas emitted from the material and the lighter triggered the blast. Firemen spent two hours dousing the flames. The three men were taken to Northern Hospital where Yip was in a critical condition with burns to the left side of his body. His 64-year-old colleague was in a serious condition. The driver was discharged after treatment.