Republican leaders in both chambers are raising sharper questions about the White House’s involvement in the controversial “Fast and Furious” program after President Obama invoked executive privilege to withhold documents from Republican investigators.

Both the White House and U.S. Attorney General Eric Holder have claimed repeatedly that high-level officials – both in the Department of Justice and in the White House – were unaware of the nature of the botched program, which put firearms into the hands of known gun-runners in an effort to trace them to drug-smugglers along the Mexican border.

“How can the president assert executive privilege if there was no White House involvement? How can the president exert executive privilege over documents he’s supposedly never seen?” Grassley, who met with Holder Tuesday night, said Wednesday in a statement. “Is something very big being hidden to go to this extreme? … The questions from Congress go to determining what happened in a disastrous government program for accountability and so that it’s never repeated again.”