I hope they are found safe and well, but the posters who mention the drug issues in the area are correct. The sad fact is the balance of probabilities is weighted towards four young lads enjoying a weekend of freedom, potentially drunk or high, driving like they're invincible - as many do when they're young and newly allowed on the roads - and coming unstuck on the mountain roads.
But just because that's probable doesn't make it definite. There is certainly a chance they've wandered off and got lost, and they have nothing more than a good story to show for it. But four 17 year olds on their own with a car and inexperienced driver in the mountains after telling their parents they were elsewhere and all dropping out of contact simultaneously is not normally a recipe for a happy ending.