U.S. federal authorities arrested two Portland State University students yesterday and are seeking two others in conjunction with the firebombing of logging trucks during last year’s protest of the Eagle Creek timber sale in Oregon. Environmentalists spent years protesting the timber sale, and some resorted to tree-sitting and other forms of civil disobedience. The sale was finally cancelled last April — but before that, in the early hours of June 1, 2001, a firebomb exploded under a logging truck belonging to Ray A. Schoppert Logging, destroying the vehicle and mangling two others. No one was injured, but damages reached $50,000. Of the two people still being sought by authorities, one is Michael Scarpitti, better known as Tre Arrow, who became locally famous two years ago when he spent 11 days perched on a ledge of the U.S. Forest Service’s headquarters in downtown Portland to protest the Eagle Creek sale. Arrow’s friends expressed skepticism about his alleged involvement in the firebombing, and so far, the Portland FBI’s Joint Terrorism Task Force has declined to discuss its evidence.