A conservative activist who has caused problems for the community organizing group ACORN and the son of a federal prosecutor were among four people arrested and accused of trying to interfere with phones at U.S. Sen. Mary Landrieu's office.

Activist James O'Keefe, 25, was already in Landrieu's New Orleans office Monday when Robert Flanagan and Joseph Basel, both 24, showed up claiming to be telephone repairmen, according to U.S. Attorney Jim Letten's office. Letten says O'Keefe recorded the two with his cell phone.

Once inside the reception area, Flanagan, the son of acting U.S. Attorney Bill Flanagan in Shreveport, and Basel asked for access to the main phone at the reception desk.

After handling the phone, "Flanagan and Basel next requested access to the telephone closet because they needed to perform work on the main telephone system," Letten's office said.

The men were directed to another office in the building, they're accused of again misrepresenting themselves as telephone repairmen.

They were arrested later by the U.S. Marshal's Service. Details of the arrest were not available. A fourth man, Stan Dai, 24, was also arrested, but Letten's office said only that he assisted the others in planning, coordinating and preparing the operation.

Federal officials did not say why the men wanted to interfere with Landrieu's phones or whether they were successful. Landrieu, a moderate Democrat, declined comment Tuesday. She has been in the news recently because she negotiated an increase in Medicaid funds for her state before announcing her support for Senate health care legislation.

An FBI criminal complaint charging the men was unsealed Tuesday.

O'Keefe was the brains behind a series of undercover videos which have caused major problems for ACORN _ the Association of Community Organizers for Reform Now.

O'Keefe managed to do what Republicans have been trying to do for years _ hurt the political affiliates of ACORN, which have registered hundreds of thousands of voters in urban and other poor areas of the country.

By producing undercover videos shot in ACORN offices, O'Keefe brought a firestorm of criticism that the group was helping its low-income clients break the law.

Using a hidden camera, O'Keefe, accompanied by a young woman posing as a prostitute, shot videos in various ACORN offices where staffers appeared to offer illegal tax advice and to support the misuse of public funds and illegal trafficking in children.

O'Keefe once was editor of a conservative magazine on the campus of Rutgers University in New Jersey, according to the Newark Star-Ledger.

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Associated Press Writer Pete Yost in Washington contributed to this report.