Washington ( CNN ) -- The House may have voted contempt charges against Attorney General Eric Holder , but that has not ended the investigation into who at the Justice Department knew about Operation Fast and Furious -- and when . Tuesday , Sen. Charles Grassley , R-Iowa , sent a letter to Holder demanding to know who at the Justice Department was aware of a Bureau of Alcohol , Tobacco , Firearms and Explosives memo on questionable tactics , which was forwarded to ATF headquarters and possibly to the Justice Department one day before Justice sent a faulty letter to Grassley denying any `` gunwalking . '' `` Which DOJ personnel received a copy of the February 3 , 2011 memorandum before the February 4 , 2011 reply was sent to me ? '' Grassley demanded to know . Grassley said information he has received , apparently from whistleblowers , indicated the memo questioning Fast and Furious from ATF field agent Gary Styers had caused a stir at ATF headquarters . `` It has been alleged individuals within the Deputy Attorney General 's office and Office of Legislative Affairs at the Department were aware of or actually read the memorandum before the Department 's February 4 , 2011 letter was sent , '' Grassley said . Grassley said he wants answers and any relevant documents no later than July 17 , 2012 . The issue is significant because the February 4 letter from Justice denied any `` gunwalking '' of illegally purchased firearms that had made their way across the Mexican border to drug cartels . But the Justice Department 10 months later had to admit to Congress that letter was wrong , and it was formally withdrawn by senior Justice officials . A senior Justice Department official familiar with the Grassley letter when asked for reaction said only , `` We will respond appropriately . ''
Bush : ` ` We must respond appropriately , '' says a Justice Department official . Sen. Grassley 's campaign demands answers from Attorney General Holder . At issue is a February 2011 memo that includes a DOJ letter to Sen .