Joe Biden’s efforts to quell a controversy over classified documents in his private possession became more difficult after aides discovered a second set, a development that will intensify scrutiny of the U.S. president.

The revelation, reported Wednesday by NBC News and the New York Times, that records were found at a separate location from the first set are likely to prompt tough questions for the White House and fuel criticism from Republicans — even though they dismiss more serious accusations against former U.S. President Donald Trump.

While the different approaches taken by Trump and Biden toward the documents have made it hard for Republicans to draw an equivalence, the string of discoveries will raise pressure on the White House to answer questions it has dismissed.