Senate Committee looking into the purging of the prosecutors

Even if they have to supoena the prosecutors themselves:

The committee has scheduled a hearing on the U.S attorney firings for 10 AM Tuesday; it's unclear, however, whether the four U.S. attorneys already subpoenaed by the House Judiciary Committee to testify Tuesday afternoon would accept the Senate committee's request. If they did not, the committee would vote Thursday on whether to issue the subpoenas.

In addition to the four former U.S. attorneys subpoenaed by the House (San Diego's Carol Lam, Seattle's John McKay, Nevada's David Iglesias and Arkansas' Bud Cummins), the Senate also sent letters to Nevada's Daniel Bogden and Arizona's Paul Charlton. All six attorneys reportedly received positive performance reviews from the Justice Department sometime before being fired.