OSLO, Jan 22 (Reuters) - A truckload of burning cheese has closed a road tunnel in Arctic Norway for the last six days. Some 27 tonnes of flaming brown cheese (brunost), a Norwegian delicacy, blocked off a three-km (1.9 mile) tunnel near the northern coastal town of Narvik when it caught fire last Thursday. The fire was finally put out on Monday. "This high concentration of fat and sugar is almost like petrol if it gets hot enough," said Viggo Berg, a policeman.