US President Joe Biden signed an executive order on Friday calling for the declassification of some documents related to investigations carried out by the FBI on the 9/11 terrorist attacks in the US.

President Biden released a statement regarding the order saying that he made a campaign promise to ensure transparency regarding the attacks. This year marks the 20th anniversary of the attacks and in recognition of that Biden said he was “honoring” his commitment to release some documents. The order will require the FBI and other federal agencies to review all records regarding individual subjects, and in particular their “connection to an agency relationship with a foreign government.”

The group 9/11 Families United issued a statement following the president’s order saying they were “thrilled” with the order and welcomed “the release of more evidence.” Last month, the group had issued an opinion piece urging the president to release more documents about the attacks. The group is concerned about “the role the kingdom of Saudi Arabia played in giving substantial support for the murderous Sept. 11, 2001, terrorist attacks.”

The order requires the agencies involved to complete their declassification reviews within the next six months.