The husband of an American woman who has been missing since 2009 and their two sons were killed Sunday in an explosion at a home in Washington state, police said. The explosion occurred soon after a social worker dropped the boys off at the home of their father Josh Powell in the town of Graham, Washington, for a supervised visit. The social worker “was forced out, and an explosion happened shortly thereafter,” said Ed Troyer, spokesman for the Pierce County Sheriff’s Office. All three bodies were recovered, and investigators were awaiting a report from the medical examiner’s office, police officials said. Susan Powell was reported missing in December 2009. Her husband Josh told police she had gone missing during a desert camping trip in the state of Utah. Josh Powell has been a person of interest in the case, but was not arrested. However, last week, a judge ordered that Powell’s sons, Charlie, 7 and Braden, 5, remain in the custody of their grandparents, Chuck and Judy Cox.