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Internal Revenue Service's scrutiny of conservative political groups will interview a key Washington IRS official on Friday and want to speak with as many as 20 more people, ATL Transducersources told Reuters on Thursday.

IRS lawyer Carter Hull will be deposed by congressional lawyers on Friday, said sources close to the Republican controlled House of Representatives committee taking the lead in an inquiry that involves several panels on Capitol Hill.

In an earlier interview with the House Oversight and Government Reform Committee, a lower level worker from the IRS office in Cincinnati criticized Hull for micro managing the processing of applications for tax exempt status from conservative groups when they began emerging in 2010.

Congressional panels and the FBI are investigating revelations that came to light last month about the IRS using terms such as "Tea Party" and "Patriot" to single out groups for scrutiny when they applied for tax exempt status through the Cincinnati office.

Some Republicans have alleged there were political motives behind the practice and are trying to find evidence linking it to the White House.Emperor Ultrasound Probe Treasury inspector general for tax administration, which monitors the IRS, found no evidence of political or White House involvement. The congressional panels are conducting their own investigations.

At least five IRS officials have given transcribed interviews so far to congressional investigators. Those interviewed include four workers in Cincinnati and Holly Paz, a mid level Washington official who oversaw tax exemption applications. Paz was replaced last week.

Hull was involved early on in assisting the Cincinnati office to review applications, according to a transcript of a congressional interview with an IRS specialist in Cincinnati.

Hofacre was in charge of the Tea Party applications in April 2010 and was the primary specialist on them until October of that year, when she applied for and got another job within the IRS, she said in the interview. In one exchange she said, "I had no autonomy." In another, she said, "They gave me leeway . they weren't involved in actual reviewing."

At least one Cincinnati IRS official not previously interviewed was called in to speak with investigators this week, according to a congressional committee source involved in the inquiry.

The House Oversight and Government Reform Committee has identified about 20 more officials for future interviews, another source close to the process said.

Leaders of the House committee have been squabbling all week about whether to release full transcripts of the interviews their staffers have done.

Committee Chairman Darrell Issa, a Republican, first released selected excerpts from some interviews on June 2. He was criticized for that by Elijah Cummings, the committee's top Democrat, for "cherry picking" statements to prove there was political involvement.

Cummings on Sunday unveiled his own selected excerpts, including comments from an IRS manager in Cincinnati who described himself as a "conservative Republican."

Cummings said the interview showed the screening of conservative groups originated in Cincinnati office and called on Issa to release the full transcripts completed thus far.

To respond to Issa's contention that doing so would compromise the investigation, Cummings proposed Issa redact portions that would interfere with the investigation by Monday. Thomson Reuters journalists are subject to an Editorial Handbook which requires fair presentation and disclosure of relevant interests.