ALBUQUERQUE, N.M. (AP) — Workers had to evacuate the U.S. government’s only underground nuclear waste repository after finding a container of waste misaligned inside its packaging, but officials confirmed Friday that no radiation was released.

It marked another problem for the New Mexico facility where a drum of radioactive waste leaked in 2014 and shut down operations for nearly three years. The leak highlighted safety concerns and resulted in a costly recovery and sweeping changes in the way low-level nuclear waste destined for the dump is treated and handled.

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In the latest incident, the contractor that runs the Waste Isolation Pilot Plant activated its emergency operations center after discovering the misaligned container Thursday night. Officials later determined conditions were stable and deactivated emergency operations.

Donavan Mager, a spokesman with Nuclear Waste Partnership LLC, said Friday that officials are investigating how the problem occurred.

In disposing the waste, seven 55-gallon drums are wrapped together in a tight formation to go deep inside the ancient salt formation where the repository is located. The idea is that the shifting salt will eventually entomb the waste.

Workers found one drum wasn’t aligned with the six others that made up the waste package. Work was immediately halted.

Procedures call for officials to develop a plan to re-enter the underground portion of the repository to deal with the pack of drums. It was not immediately known how long that would take.

“The plan is developed with extreme conservatism to ensure workers are protected,” Mager said.

Shipments to the repository resumed in 2017 following the lengthy closure stemming from the container of waste that was improperly treated at Los Alamos National Laboratory, also in New Mexico.

The repository has been receiving several shipments a week of waste that includes gloves, clothing, tools and other debris contaminated by plutonium and other radioactive elements. The Cold War-era waste was generated over years of bomb-making and nuclear weapons research.

The shipments are coming from Los Alamos lab and installations in Idaho, Tennessee, South Carolina and Texas.