Two military personnel were killed and 10 injured when a British air force helicopter crashed near an army base in northern England, officials said Thursday. North Yorkshire Police said some of the injured were in serious condition at nearby hospitals. The Sea King helicopter was carrying nine army personnel and three Royal Air Force crew when it came down late Wednesday near Catterick Garrison, a large army base. The helicopter crashed in a wooded area about 240 miles (385 kilometers) north of London, Royal Air Force spokesman Michael Mulford said. He said the helicopter was helping the army as part of an exercise at Catterick, the site of the army's Infantry Training Center.