Mo Farah has reportedly been questioned by anti-doping officials as part of an investigation into claims of wrongdoing by coach Alberto Salazar.
It has been alleged that Salazar encouraged doping among his athletes at the Nike Oregon Project in Portland.
Farah, who won the 3,000m at the Anniversary Games at the Olympic Stadium on Friday, has repeatedly distanced himself from these suggestions.
According to BBC Sport, however, the Briton was quizzed by the US Anti-Doping Agency on Saturday as part of an ongoing investigation.
Farah is said to have been interviewed for five hours by USADA lawyer Bill Bock, although there are no suggestions that the double Olympic champion is himself under investigation at this stage.
