US President Joe Biden on Friday ordered the department of justice to review documents from the FBI’s probe into the September 11, 2001, attacks for declassification and release.

“When I ran for President, I made a commitment to ensuring transparency regarding the declassification of documents on the September 11, 2001 terrorist attacks on America,” Biden said. “As we approach the 20th anniversary of that tragic day, I am honouring that commitment.”

The order requires US attorney-general Merrick Garland to make the declassified documents public over the next six months as it oversees “a declassification review of documents” related to the FBI probe. Family members of victims of the September 11 attacks asked a US government watchdog on Thursday to investigate their suspicions that the FBI lied about or destroyed evidence linking Saudi Arabia to the hijackers.

The request in a letter to department of justice inspector-general Michael Horowitz said “circumstances make it likely that one or more FBI officials committed willful misconduct with intent to destroy or secrete evidence to avoid its disclosure.”

Relatives of the victims have been pushing for years for more information about what the FBI discovered in its probe. Last month, many families asked Biden to skip 20-year memorial events unless he declassified documents they contend will show Saudi leaders supported the attacks.

Three days later, the justice department said in a court filing that it had decided to review earlier claims of privilege it had made about why it could not release information.