Several Republican members of Congress forwarded constituents' letters to the Internal Revenue Service claiming the NAACP had veered into political advocacy, a potential violation of the civil rights group's tax-exempt status, according to documents released by the NAACP.

The IRS began looking into the Baltimore-based National Association for the Advancement of Colored People about a month before the 2004 presidential election after a speech by NAACP Chairman Julian Bond that was largely critical of President Bush's policies.

Political campaigning is prohibited under the NAACP's tax-exempt status. The IRS said its inquiry would focus on whether Bond's speech was too political, and that the investigation is among dozens into the activities of tax-exempt groups during the 2004 election season.

The NAACP received more than 500 pages of documents the IRS has gathered to begin its inquiry and posted them on its Web site. The group had made requests under the Freedom of Information Act.

The documents include letters that members of Congress sent to the IRS on behalf of their constituents. The lawmakers include Sens. Lamar Alexander of Tennessee and Susan M. Collins of Maine, Rep. Jo Ann Davis of Virginia, the late Sen. Strom Thurmond of South Carolina and former Reps. Larry Combest of Texas and Joe Scarborough of Florida. All are Republicans.

Spokespeople for those members of Congress still in office said they simply forwarded the concerns of their constituents, as they would for any constituent, and took no position on the issue.

"When we get letters like this, we pass them along to the appropriate agency without taking a position on them," said Harvey Valentine, a spokesman for Alexander.

"Senator Collins never asked for a probe into the NAACP's tax status," said Jen Burita, Collins' communications director.

The NAACP has called the IRS audit a political smear campaign. Marcus Owens, an attorney for the NAACP, said the letters from Republican politicians raised questions about the motivation of the IRS probe.

"It's clear that the NAACP drew a lot of criticism and complaints from the Republican Party and many of the complaints don't have a lot of substance to them," he said. "The circumstances of the audit came just weeks before the election, and apparently they were triggered from members of the Republican Party at some level."

The chief fundraiser to Maryland Gov. Robert Ehrlich wrote a letter asking for an IRS investigation shortly after the 2000 presidential campaign, the documents showed. Ehrlich was a congressman at the time.

Richard Hug said his letter was prompted by a television ad sponsored by the NAACP's National Voter Fund. In it, the daughter of James Byrd, a black man dragged to death by three white men in a pickup truck, faulted then-Texas Gov. George W. Bush for refusing her pleas for a hate-crime law.

"I was acting as a citizen, and I think that everyone else ought to be concerned if they have nonprofit status and they are using political ads," he said Wednesday.

In a report issued in February, the IRS said it found some level of prohibited political activity in nearly three-quarters of the 82 examinations it had completed by that point into the conduct of churches and other tax-exempt groups during the 2004 elections. The IRS said that in most cases the prohibited actions were isolated cases that the agency addressed through letters to the organizations.