ALBUQUERQUE, N.M. (AP) — Los Alamos National Laboratory packed 57 barrels of nuclear waste with a type of kitty litter believed to have caused a radiation leak at the federal government’s troubled nuclear waste dump, posing a potentially “imminent” and “substantial” threat to public health and the environment, New Mexico officials said Monday.

State Environment Department Secretary Ryan Flynn issued a formal order giving the lab two days to submit a plan for securing the waste containers, many of which are likely stored outdoors on the lab’s northern New Mexico campus or at temporary site in west Texas.