(CNN) -- U.S. Attorney General Eric Holder has ordered an investigation into Internal Revenue Service political targeting of some conservative groups, he announced Tuesday.
"The FBI is coordinating with the Justice Department to see if any laws were broken," he told reporters.
Even if none were, the actions "were certainly outrageous and unacceptable," he said.
The IRS has admitted that members of its Cincinnati office engaged in such activity. But documents suggest at least three other IRS offices did the same.
Letters provided to CNN show IRS officials in Washington and California contacted conservative groups to demand more information before approving the groups' requests for tax-exempt status.
The American Center for Law and Justice, a legal group representing numerous conservative organizations, provided CNN with four such letters: one each from IRS offices in Washington; Cincinnati; El Monte, California, and Laguna Niguel, California.
The words "patriots" or "tea party" figured in the names of each group that received the letter.
The IRS did not respond to CNN's request for comment regarding the letters.
Lois Lerner, director of tax exempt organizations for the IRS, said Friday that the IRS had targeted some groups for further review because they had those words in their names.
She said the activity took place at the IRS office in Cincinnati that handles most applications for 501(c)(4) status.
A draft report from the inspector general for the IRS obtained by CNN says agents were on the lookout to give special scrutiny to groups with "tea party" and "patriots" in their names as well as groups that had made statements criticizing "how the country is being run."
The report says in January 2012, the criteria was revised as "political action-type organizations involved in limiting/expanding government, educating on the Constitution and Bill of Rights, social economic reform/movement."
The report also says IRS officials knew about the targeting of conservative groups in June 2011 -- and that the practice began as early as March 2010.
White House 'confident' of no involvement
White House spokesman Jay Carney told reporters Tuesday that he's "confident" no one at the White House was involved in the practice.
Asked about complaints by some Republican lawmakers for the past couple of years that conservative groups were being unfairly targeted, Carney said he is "sure some people knew about the stories. But we were not aware of any activity or any review by the inspector general."
Obama on Monday called the IRS' alleged actions "outrageous" and said personnel involved "have to be held accountable." Some Republicans criticized the president for not speaking out on the issue immediately. He said he learned about it through news reports Friday.
Lawmakers on both sides of the aisle have expressed outrage as well and multiple congressional probes are under way.
The Republican-led House Ways and Means Committee, which oversees the IRS, announced it will hold a hearing Friday. Slated to testify are Steve Miller, the acting IRS commissioner; and the Treasury inspector general investigating the complaints, J. Russell George.
In the Senate, Finance Committee Chairman Max Baucus called for a full investigation as well.
"We need to know who knew what, and exactly what mistakes were made," said Baucus, D-Montana. "The American people have questions for the IRS and I intend to get answers."
Rep. Darrell Issa, R-California and chairman of the House Oversight and Government Reform Committee, told CNN's "The Situation Room" that he and his colleagues have a full plate of concerns to look into and that the IRS is one of them.
Sen. Carl Levin, D-Michigan, said the Permanent Subcommittee on Investigations -- which he chairs -- now needs to expand an investigation already under way.
That one has focused on the IRS's "failure to enforce the law requiring that tax-exempt 501(c)4s be engaged exclusively in social welfare activities, not partisan politics," he said in a statement. The IRS' announcement about targeting of some conservative groups raises questions over its impartiality in doing so, he added.
Sen. Marco Rubio, R-Florida, demanded the resignation of the IRS commissioner in a letter to Treasury Secretary Jack Lew on Monday, noting the agency "cannot operate with even a shred of the American people's confidence under the current leadership."
Miller assumed the role of acting head of the IRS last November. The previous commissioner, Douglas Shulman, was appointed by President George W. Bush. Shulman testified at a March 2012 congressional hearing that his agency did not target conservative groups for political reasons.