BOULDER, Colo. — Court documents in a pending lawsuit against the U.S. Fish and Wildlife Service say trails at the Rocky Flats National Wildlife Refuge in northern Colorado will be closed until at least Sept. 15.

The Daily Camera reported Wednesday that a group of plaintiffs hopes to keep the refuge closed until a judge decides the merits of the case.

Environmental activists filed a lawsuit against the agency in May.

The suit claims the agency hasn't conducted required testing to prove that the refuge at the site of a former nuclear weapons facility is safe for public visits.

The agency says studies by the Environmental Protection Agency and Colorado Department of Public Health and Environment show the site is safe.

Activists say a new study of the area is needed.