CARLSBAD, N.M. (AP) -- Shipments of certain kinds of nuclear waste from Los Alamos National Laboratory to a temporary storage facility in West Texas have been halted while investigators try to identify the cause of a radiation release at the federal government's underground repository in southeastern New Mexico.
The U.S. Department of Energy announced Friday that the shipments were being put on hold to ensure the protection of workers, residents and the environment.
Investigators have been making trips into the underground repository in an effort to determine what caused a release of radiation on Feb. 14 that affected some workers and forced the closure of the Waste Isolation Pilot Plant.
Based on those trips, Department of Energy officials said the team is evaluating the contents of a set of drums in the area where the release occurred. Those drums came from Los Alamos.
"The team is looking at the possibility that a chemical reaction may have occurred within a drum, causing a potential release," the department said in a statement.
Investigators are also looking at whether the cause could be related to the waste packages themselves.
The shipment of this specific kind of waste from Los Alamos is not expected to resume until investigators know more.
Los Alamos has been sending nuclear waste to Texas for nearly a month because of the closure of the Waste Isolation Pilot Plant, the federal government's only permanent repository for waste from decades of nuclear-bomb building.
The Los Alamos lab is under a tight deadline to get the waste off its northern New Mexico campus before wildfire season peaks. The state of New Mexico pressured Los Alamos to speed up removal of the waste after a massive wildfire in 2011 lapped at the edges of lab property.
The Waste Isolation Pilot Plant's closure left federal officials scrambling to find an alternative for the last of nearly 4,000 barrels of plutonium-contaminated tools that Los Alamos has promised to have removed from outdoor storage on its northern New Mexico campus by the end of June.
Los Alamos began shipping the waste to West Texas for temporary storage in early April.
Joe Franco, the head of the Department of Energy's Carlsbad Field Office, said in a letter to the community Friday that progress is being made at the underground dump and officials are gaining more clarity about what happened on Feb. 14. As more details come in, the recovery plan is being refined, he said.