The probe was disclosed in a recent report circulated within the Nuclear Regulatory Commission.

The NRC hosts the electronic library of Yucca Mountain documents that are pertinent to the Energy Department's bid for a license to build a nuclear waste repository in Nevada.

A Jan. 25 report from library administrator Dan Graser said the NRC was informed the Energy Department inspector general was investigating the discovery of "prohibited access, non-official business documents" submitted by DOE for the database.

Contacted Friday, Graser declined to discuss what was found or what was being investigated.

"As far as I know, it is still ongoing within the DOE IG office," Graser said of the probe.

A spokeswoman for Inspector General Gregory Friedman said she would not confirm or deny the report.

Ward Sproat, director of the DOE Office of Civilian Radioactive Waste Management that runs the Yucca project, said Monday he was unaware of any document investigation.

Sproat said he met with Friedman on Thursday on other matters, "and he mentioned absolutely nothing about it."

The electronic library, called the licensing support network, contains more than 3.5 million documents pertaining to the proposed nuclear waste repository about 100 miles northwest of Las Vegas.

Attorneys for the state of Nevada have complained to the NRC that the database is "enormously bloated" with multiple copies of documents, empty e-mails, clearly obsolete content and employee personal e-mails.

Graser said the investigation is unrelated to that content.

"It is none of that stuff," he said. "Those are not the sorts of things the inspector general investigates."

Contact Stephens Washington Bureau Chief Steve Tetreault at stetreault@stephensmedia.com or (202) 783-1760.