WASHINGTON - Five Transportation Security Administration employees have been placed on administrative leave since it was discovered that sensitive guidelines about airport passenger screening were posted on the Internet.

The move was disclosed as senators questioned administration officials yesterday about the second embarrassing security flap at the Homeland Security Department in as many weeks.

The Secret Service, also part of the sprawling department, is investigating how a couple of would-be reality-TV stars were able to get into a White House state dinner without an invitation.

Assistant Homeland Security Secretary David Heyman told senators yesterday that a full investigation into the Internet security lapse is under way and the TSA employees have been taken off duty pending the results of that probe.

He did not say how many employees were put on leave. A TSA official who spoke on condition of anonymity because of the investigation said five employees were placed on administrative leave Tuesday.

The Homeland Security Department has also stopped posting documents with security information either in full or in part on the Internet until the TSA review is complete, Heyman told the Senate Homeland Security and Governmental Affairs Committee.

Homeland Security Secretary Janet Napolitano told a hearing of the Senate Judiciary Committee yesterday that the department is taking steps to make sure this never happens again and that the department's inspector general is also investigating.

Napolitano said "the traveling public was not at risk."

The passenger-screening document was improperly on the Internet in a way that could offer insight into how to sidestep security.

"Even what appeared to be an innocent posting to help federal contractors can have serious consequences for our security," Sen. Susan Collins (R., Maine) said.

Heyman said he did not know who at TSA signed off on putting the document on the Web.

The TSA removed the document from the Internet on Sunday after the lapse was reported on a blog, but copies - with the redacted portions exposed - remain posted on Web sites not controlled by the government.

Among many sensitive sections, the document outlines who is exempt from additional screening measures, including members of the U.S. armed forces, governors and lieutenant governors, the mayor of Washington, and their immediate families.

It also offers examples of identification documents that screeners accept, including congressional, federal air marshal, and CIA ID cards; and it explains that diplomatic pouches and certain foreign dignitaries with law enforcement escorts are not subjected to any screening at all.

TSA said the document is outdated. It was posted in March by TSA on the Federal Business Opportunity site. The posting was improper because sensitive information was not properly protected, TSA spokeswoman Kristin Lee said.

As a result, some Web sites, using widely available software, were able to uncover the original text of sections that were blacked out. On Sunday, the blog Wandering Aramean pointed out the document in a posting titled, "The TSA makes another stupid move."