Washington ? The government’s inadvertent and red-faced Internet posting of a 266-page list of U.S. nuclear sites provided a one-step guide for anyone wanting details about such sensitive information.

Obama administration officials said Wednesday the document contained no classified material about nuclear weapons. They contended the locations and other details already were available from public sources.

Energy Secretary Steven Chu said “a snafu” led to the online posting. “A little embarrassing,” he acknowledged.

The document, stamped “highly confidential safeguards sensitive,” made it onto the Government Printing Office’s Web site — and why that happened was not immediately clear. A newsletter that focuses on government secrecy quickly picked up on it. The printing office removed the document when informed “about the potential sensitive nature” of the list, the agency said.

By then it was too late.

The information, compiled for international nuclear inspectors, is a compilation of hundreds of civilian nuclear sites, along with maps and details of the facilities. The material includes sites for uranium storage, nuclear fuel fabrication plants and nuclear research facilities.

“It’s an easy locator for civilian sites,” Thomas D’Agostino, head of the National Nuclear Security Administration, told Sen. Bill Nelson, D-Fla., when questions about the disclosure came up at a Senate Armed Services subcommittee hearing.

“We don’t want to make this easier for people to get this kind of information. Unfortunately, something like this makes it easier,” D’Agostino said.

House Speaker Nancy Pelosi, D-Calif., said the release exposed lax safeguards. She asked congressional investigators to review the incident.

Chu said he was stepping up security at one of the sites, a storage facility for highly enriched uranium at the Y-12 Oak Ridge complex in Tennessee. “That’s of great concern,” he told the House Appropriations subcommittee when asked about the disclosure.

Oak Ridge holds large quantities of highly enriched uranium, which can be used to fashion a nuclear weapon. The department plans to move the material into $549 million high-security warehouse to be competed next year.

“There’s no secret or classified information that’s been compromised. … The sites and everything are public knowledge,” Chu told reporters.

Steven Aftergood, director of the Federation of American Scientists’ government secrecy project, which distributed the document, said he was perplexed about all the attention surrounding the disclosure.

“Some people are painting this as a road map for terrorists, which it is not,” Aftergood said. “It is simply a listing of the numerous nuclear research sites and the programs that are under way. So it poses no security threat whatsoever.”

In addition to the Y-12 facility, the document lists facilities at the Hanford nuclear site in Washington state and various civilian nuclear fuel processing sites, including one that produces nuclear fuel for the Navy.

Beth Hayden, a spokeswoman for the Nuclear Regulatory Commission, said the agency reviewed the document as it relates to civilian facilities with NRC licenses. “We are confident that information of direct national security significance was not compromised,” she said.

The NRC has jurisdiction over commercial nuclear power plants and civilian uranium processing and storage facilities.

The Government Printing Office processes and produces various congressional documents. The lengthy nuclear list was transmitted to Congress in advance of providing it to the International Atomic Energy Agency as part of a nonproliferation-related inspection program.

Some of the pages are marked “highly confidential safeguards sensitive,” a designation used by the IAEA, but not the U.S. government.