Updated

Federal officials Thursday confirmed a leak of nuclear waste at a southeastern New Mexico repository, but it could be weeks before workers can safely access the underground dump to determine what happened.

The release of radiation from the Waste Isolation Pilot Plant poses no public health threat, officials emphasized, but the state environment secretary said he was concerned with the lag in getting information about the incident.

The DOE on Saturday announced that it had shuttered operations in response to an underground radiation sensor. But it wasn't until Wednesday night that DOE confirmed that radiation had also been released above ground, about a half mile from the plant.  And it wasn't until a Thursday press conference that Jose Franco, manager of the DOE's Carlsbad Field Office, confirmed publicly that readings from the monitors matched materials from the waste that is stored there, indicating a leak.

Environment Secretary Ryan Flynn said he traveled to Carlsbad as soon as he was told Wednesday night that radiation had been picked up by an above ground air sensor.

"We are wondering why it took a couple of days to confirm the radiological event outside of the underground," he said. "We will demand that federal officials share information with the public in real time. That's the reason we are here."

Franco said it was the first such incident since WIPP opened 15 years ago, and that the emergency systems worked flawlessly after the alert late Friday night. He said the filters activated immediately, enabling only trace amounts of radiation to escape. The radiation levels underground have since been dropping, he said, indicating it was an isolated spill.

Flynn, however, said, "Events like this should never occur. From the state's perspective, one event is far too many. Our primary concern continues to be public safety."

"Even though the levels detected are very low," he said, "radiation is simply not supposed to be released outside the building."

The DOE has appointed a team to investigate the leak at the plant.

It was the second incident in just a matter of weeks. Earlier this month, a truck hauling salt below ground caught fire, shutting operations for a few days. Officials have not said what caused the truck fire, but Franco said it was unlikely the events were related. He also said there was no evidence of a seismic event at the site.

WIPP is the nation's first underground nuclear repository. Each week it receives 17 to 19 shipments of low-grade nuclear waste like plutonium-contaminated clothing and tools from Los Alamos National Laboratory and other federal nuclear sites around the country.

Those shipments have been halted indefinitely, which could impact the ability of Los Alamos to meet a state deadline this year for removing thousands of barrels of waste that currently are stored outside on its northern New Mexico compound.

After a large wildfire lapped at the edges of lab property in summer 2011, New Mexico Gov. Susana Martinez identified removal of the waste as a top priority.