CNN reports that it has confirmed that the Steel dossier on Russian ties to Donald Trump's campaign was part of its evidence to gain a secret court order.
The FBI last year used the dossier to win approval to secretly monitor a Trump associate, US officials told CNN.
The network said the dossier has also been cited by FBI Director James Comey in some of his briefings to members of Congress.
A Foreign Intelligence Surveillance Act (FISA) order was gained to monitor the communications of Carter Page, a Trump campaign adviser last year on national security.
CNN reported: "Officials familiar with the process say even if the application to monitor Page included information from the dossier, it would only be after the FBI had corroborated the information through its own investigation. The officials would not say what or how much was corroborated".