Were they plannin' a pressure-cooker type bomb?... Middle Eastern Men Arrested Near Mexican Border with Steel Cylinders DECEMBER 04, 2015 - Five young Middle Eastern men were apprehended by the U.S. Border Patrol this week in an Arizona town situated about 30 miles from the Mexican border, law enforcement and other sources told Judicial Watch.
Probably just as clubs. The tubes would be the easiest ingredient to obtain for pipe bombs so... just clubs.
Or water canteens? Mine is stainless steel, and its cylindrical. The authorities seemed to think they didn't pose a threat after being them...