The Government Accountability Office has accepted a request by a group of U.S. senators to investigate the activities of President Donald Trump’s commission on voter fraud.

Last week, Democratic Sens. Michael Bennet of Colorado, Cory Booker of New Jersey and Amy Klobuchar of Minnesota had written the agency to request the investigation, citing a lack of transparency surrounding the Presidential Advisory Commission on Election Integrity.

The senators said in a statement Thursday that the GAO investigation would begin in about five months.

The Trump commission has stirred controversy from the moment it was established last spring. Critics say Trump is using it to find support for his unsubstantiated claims of widespread voter fraud that cost him the popular vote during the 2016 election.

Last week, two members of the commission sent letters complaining of a lack of information about the panel’s work.