Top Republicans on the House Oversight and Government Reform Committee have asked the inspector general of the Internal Revenue Service to examine reports that the agency not only targeted conservative groups seeking tax-exempt status, but gave additional scrutiny to conservative organizations that already qualified for such status “based on their political beliefs or ideology.”

In a letter sent Monday to J. Russell George, the Treasury Department’s Inspector General for Tax Administration, committee Chairman Darrell Issa, R-Calif., and subcommittee Chairman Jim Jordan, R-Ohio, said they have learned of “questionable treatment” of some right-leaning groups by the IRS.

In May, George released a report that found the IRS had singled out for special scrutiny groups with names that included “Tea Party,” “Patriot,” “9/12 and other conservative-sounding monikers, that were applying to the tax agency for an exemption from federal taxes.

Issa and Jordan’s letter cites examples involving two conservative groups already awarded tax-exempt status: The Arlington-based Leadership Institute, audited by the IRS in 2011 and 2012 for activities in 2008, and the Herndon-based Clare Boothe Luce Policy Institute, audited in 2011.

In each case, the audits took months and cost ten of thousands of dollars. Agents requested lists of contributors and, in the case of the Leadership Institute, “information about its interns and where they worked after their internships.”

The audits appear to have crossed referenced the agency’s special scrutiny of conservative groups seeking tax exempt status.

“In at least one instance, a Tea Party group applying for tax exempt status…received an information request letter from the IRS asking about its affiliation with the Leadership Institute.”

Issa and Jordan told George they are “troubled by the evidence that IRS may have conducted unnecessary audits and systematic post-hoc reviews of entire groups” who have long ago qualified for tax exempt status.