Activists are asking a judge to make documents public from a 27-year-old criminal investigation into a former nuclear weapons plant outside Denver.
The activists said Thursday that the documents could show whether the federal government did enough to clean up the site before turning part of it into a wildlife refuge and opening it to the public.
The Rocky Flats plant made plutonium triggers for nuclear bombs until 1989, when it was shut down after a series of fires and accidental releases.
After a grand jury investigation, the plant operator pleaded guilty to environmental violations and was fined $18.5 million. The grand jury records are still sealed.
The site was cleaned up but remains off-limits. A buffer zone around the plant became a wildlife refuge and opened to visitors last fall.