I scoured the tunnels but found the most in the tunnels N and S of the White House on the borders of that area. Watch the walls and doors with red lights over them can be opened is what I have found.. The tunnels south of WH are fairly extensive. Unfortunately I got really unlucky in all the tunnels I have searched. I have 13 keys and not one of them is a Hyena key. I am set for Sons and Outcast though.