A decades-old toxic chromium plume from Los Alamos National Laboratory has migrated onto San Ildefonso Pueblo land, the New Mexico Environment Department announced Thursday.

There is “no imminent threat to drinking water” on the pueblo or in Los Alamos County, the Environment Department said in a statement.

But the new groundwater testing results “are conclusive evidence that the U.S. Department of Energy’s efforts to contain the chromium plume have been inadequate,” said Bruce Baizel, the Environment Department’s director of compliance and enforcement.

“While drinking water supplies are safe for now, the U.S. Department of Energy must take immediate and definitive actions to protect drinking water,” Baizel said in a statement.

The Department of Energy said Friday it “remains committed to remediating the hexavalent chromium plume at Los Alamos National Laboratory.”

“We are proactively assessing, monitoring, and collaborating,” with the state Environment Department, state Office of the State Engineer and Pueblo de San Ildefonso, the spokesperson continued, adding the Department of Energy agrees with the state’s assessment the plume is “not currently near any known public or private drinking water wells.”

Hexavalent chromium is a known carcinogen that, when ingested in drinking water, can harm the liver, kidneys and reproductive systems and, some research suggests, can cause stomach cancer.

Lab workers between 1957 and 1972 dumped water from an old power plant’s cooling towers that had been funneled through steel pipes laced with hexavalent chromium into Sandia Canyon. From there, the water traveled several miles to Mortandad Canyon and pooled about 1,000 feet underground in a huge plume the lab discovered in the early 2000s.

The plume’s boundary has been fuzzy — a 15-member independent review team that studied the chromium plume released a report early this year stating a “small portion” of the plume had possibly already reached or passed into San Ildefonso Pueblo.

The recent groundwater sampling on pueblo land found hexavalent chromium at levels ranging from 53 to 72.9 micrograms per liter, according to the news release — above the groundwater standard of 50 micrograms per liter.

The pueblo, the State Engineer’s Office and the Environment Department are working together to recommend steps including “finalizing construction of additional monitoring wells to better track the chromium plume’s migration,” according to the news release.

Additionally, the Environment Department “is pursuing civil enforcement actions against the U.S. Department of Energy related to this matter,” the release states.