Rep. Jim Kolbe, R-Ariz., took the former pages as well as staff members and National Park Service officials on a Fourth of July rafting trip in the Grand Canyon in 1996, his spokeswoman Korenna Cline said Friday.
An allegation related to the trip was given to the U.S. attorney's office in Phoenix, but it was not immediately clear whether it was related any contention of improper activity by Kolbe.
CBS News' Investigative Unit has spoken to several former pages who received or are aware of "uncomfortable" e-mails from Kolbe. However, they know of no sexually explicit e-mails from the congressman.
The official described the inquiry as preliminary and far narrower in scope than the federal investigation into former Rep. Mark Foley, R-Fla., who resigned two weeks ago amid reports about sexually explicit e-mails he sent to pages.
A second law enforcement official said the 1996 trip may be too old to investigate as a criminal action. Both officials spoke on condition of anonymity because of the ongoing investigation. A spokeswoman for the Justice Department declined comment.
Cline said the rafting party included five current staffers, two former pages and Kolbe's sister. Nothing inappropriate happened on the trip, she said. She did not know who the pages were or what year they worked for Kolbe, but she said they paid their own way.
"There is absolutely no basis and no truth to any inappropriate behavior," she said.
At the time of the trip, Kolbe served on a subcommittee that oversaw the national park system. He visited the park to look at National Park Service operations and fire reconnaissance.
Kolbe, 64, is the only openly gay Republican in Congress.
He was pulled into the unfolding scandal involving Foley when he said this week that a former page had complained in 2001 or 2002 about e-mails the page had received from Foley that made him feel uncomfortable. Kolbe said he referred the matter to the House clerk and that someone from Kolbe's office confronted Foley himself.
Kolbe, who is retiring this year after 22 years in the House, was a page from 1958 to 1960 for Arizona Sen. Barry Goldwater.
Kolbe served on the board that oversees the page program between 1995 and February 2001. He frequently offers his home to former pages, interns, constituents and colleagues visiting Washington.
He is traveling in Europe and has declined interviews. Cline said he had not hired a lawyer in the matter.