According to documents recently obtained by House investigators, the Internal Revenue Service may have been caught violating federal tax law when the agency allegedly transferred confidential information pertaining to a number of 501(c)(4) groups to the Federal Bureau of Investigation.

According to a report from the National Review‘s Eliana Johnson, the “information was transmitted in advance of former IRS official Lois Lerner’s meeting the same month with Justice Department officials about the possibility of using campaign-finance laws to prosecute certain nonprofit groups.”

Among the emails uncovered by House investigators is a conversation between Lerner and Richard Pilger, the director of the Justice Department’s election-crimes branch, in which Lerner confirms that she is preparing data for transfer to the FBI:

A letter to IRS Commissioner John Koskinen from the House Oversight and Government Reform Committee revealed on Monday that 21 disks containing over 1.1 million pages of information regarding tax-exempt groups was handed off to the FBI in October, 2010. The letter demands that the IRS produce any confidential taxpayer material transferred to the FBI.

Johnson reported:

The Justice Department never prosecuted social-welfare groups, and e-mails from IRS officials show their awareness that, as a result of the Supreme Court’s 2010 decision in the Citizens United case, which allowed unlimited amounts of money from nonprofit groups and labor unions to flow into the political process, the law did not favor a crackdown on anonymous donations to politically orientated nonprofits, which sprouted up on all sides in the wake of the ruling.

“At the very least,” the letter from the House committee chaired by Rep. Darrell Issa (D-CA) read, “this information suggests that the IRS considered the political speech activities of nonprofits to be worthy of investigation by federal law-enforcement officials.”

“The IRS apparently considered political speech by nonprofit groups to be so troublesome that it illegally assisted federal law-enforcement officials in assembling a massive database of the lawful political speech of thousands of American citizens, weeks before the 2010 midterm elections, using confidential taxpayer information,” the letter continued.