Story highlights Republicans formally ask DOJ to investigate Hillary Clinton testimony

They want to know if she lied before Congress

Washington (CNN) Two House Republican committee chairmen formally requested that the Justice Department investigate whether Hillary Clinton lied to Congress.

House Oversight Committee Chairman Jason Chaffetz and House Judiciary Committee Chairman Bob Goodlatte, sent a letter to Channing Phillips, the U.S. attorney for the District of Columbia, on Monday, asking for a new probe to determine with Clinton "committed perjury and made false statements during her testimony under oath before congressional committees."

FBI Director James Comey told Chaffetz's panel during his appearance last week that his agency's review of Clinton's handling of classified materials and use of a private email server did not cover her congressional testimony. The letter serves as an official criminal referral from Congress so that the Justice Department can open a separate investigation.

"The evidence collected by the FBI during its investigation of Secretary Clinton's use of a personal email system appears to directly contradict several aspects of her sworn testimony," said Chaffetz and Goodlatte in their letter.

Specifically, Republican lawmakers are pointing Clinton's testimony before House Select Committee on Benghazi in October 2015 when the former secretary of state stated she did not sent any classified materials over a private email server.

Read More