Wreckage after tornado in Joplin, Missouri
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Barack Obama to visit tornado ravaged Joplin

President Barack Obama is to attend a memorial service on Sunday in the city of Joplin, Missouri, devastated by a massive tornado a week ago.

Local officials say the death toll has risen to 142, with 105 people missing. Emergency services and volunteers are still searching for survivors.

Tom Burridge reports from Washington.

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