A tire blowout on a bus carrying 16 Marines to Camp Pendleton sent it plunging down a ravine and into a tree, injuring 11 people aboard, authorities said. Those hurt were treated at hospitals for minor injuries and released, San Diego city fire officials said. The passengers were recent boot camp graduates who had been on furlough and were reporting to Camp Pendleton for further training. The private shuttle bus was contracted to transport them from Lindbergh Field to the northern San Diego County military base. The accident, which occurred on northbound Interstate 5 near Clairemont Drive, tied up rush-hour traffic on the freeway for more than an hour.