A San Jose elementary school was evacuated Friday morning when a janitor found an backpack containing suspicious material, according to officials and news media reports. Bridges Academy at 1702 McLaughlin Ave., was evacuated just after 9 a.m. Police set up a perimeter around the school and called in a hazardous materials crew to investigate. The incident unfolded after a janitor found a backpack with a bottle inside that was filled with liquid and labeled “nitroglycerin,” KPIX news reported. Bill Hutchinson is a San Francisco Chronicle staff writer.