An "improvised launch device" was fired near a U.S. air base in Japan late Thursday and left-wing radicals are reportedly suspected to be behind the attack, NBC News reported. Tokyo Metropolitan Police received several reports of an explosion near Yokota Air Force Base around 11:30 p.m. local time (9:30 a.m. ET). Authorities later confirmed that a "projectile" had been fired. Police said "two pipes, a lead wire and dry batteries" were later recovered from a field about 300 yards from the military site. No injuries have been reported, a U.S. military spokesman told Reuters. National broadcaster NHK reported that left-wing activists were suspected to be involved in the attack. NBC News was unable to independently confirm the report.