New Mexico: 500 barrels of questionable nuke waste

FILE - This May 10, 2014 file photo provided by the Waste Isolation Pilot Plant shows torn and open bags of magnesium oxide on top of standard waste boxes at the WIPP site in Carlsbad, N.M. Workers at a West Texas nuclear waste disposal site are closely monitoring containers from Los Alamos National Lab, Tuesday, May 20, 2014, a day after New Mexico officials announced a type of kitty litter is believed to have caused a radiation leak at the federal government's troubled nuclear waste dump. (AP Photo/Waste Isolation Pilot Plant, File)

ALBUQUERQUE, N.M. (AP) — New Mexico environment officials say more than 500 barrels of waste from Los Alamos National Laboratory was packed with the kitty litter suspected of causing a chemical reaction and radiation release at the nation's underground nuclear waste dump.

Environment Secretary Ryan Flynn Tuesday gave the Department of Energy and the contractor that runs the Waste Isolation Pilot Plant in southeastern New Mexico until May 30 to detail plans for permanently sealing the underground rooms where more than 300 barrels of the potentially dangerous containers of waste are stored.

In addition to 368 containers at the dump, environment officials say 57 more are still at Los Alamos and more than 100 are in storage in West Texas.

The waste was packed with kitty litter to absorb moisture. Officials are investigating whether a switch from inorganic to organic litter is to blame for a February leak in February that contaminated 22 workers.