RICHLAND, Wash. (AP) - A worker at south-central Washington's Hanford nuclear reservation was seriously injured when he fell through a catwalk access door 50 feet to the ground.

Dave Brockman of the Department of Energy's Richland Operations Office told Hanford employees in a memo that the worker sustained very serious but not life-threatening injuries. He was taken to Kadlec Regional Medical Center.

The worker's name has not been released. He's described as an experienced Hanford worker who does decontamination and demolition on unneeded buildings.

Washington Closure, the contractor hired to clean up the site's Columbia River corridor, immediately stopped work at the building where the fall occurred Wednesday.

Washington Closure workers have Thursday off for the Fourth of July holiday and do not work Fridays, so work will not resume until at least Monday.