Border Patrol chopper forced down Illegal immigrants in Arizona threw rocks Thursday, August 25, 2005; Posted: 7:11 p.m. EDT (23:11 GMT) (CNN) -- Rock-throwing illegal immigrants near Yuma, Arizona, forced a U.S. Border Patrol helicopter pilot to make an emergency landing this week, the customs agency said. No one was hurt in the incident, which happened Tuesday while the pilot was helping agents on the ground apprehend 17 people attempting to illegally enter the U.S., spokesman Michael Gramley said. They were on the north side of the All-American Canal, a large irrigation canal that runs from California along the U.S.-Mexico border. While the helicopter was hovering, a group of 10 people on the south side of the canal began throwing baseball-size rocks at it, Gramley said. One rock hit a rotor, Gramley said. The pilot felt a bad vibration and made an emergency landing about a mile away. Gramley said the rock throwers were believed to be smugglers. "This type of aggressive, assaultive behavior is not something that we typically see from a migrant who's just coming to the United States to find work," he added. Authorities caught the 17 people on the north side of the canal, including two brothers, ages 15 and 17, suspected of being smugglers, Gramley said. One youth admitted throwing rocks, although he was not the one that hit the copter, Gramley said. Both teens are being processed for formal deportation, he said.