Updated

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 Friday 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 369 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.