The F.B.I. monitored Muhammad Ali and his ties to the Nation of Islam, newly released documents from 1966 show.

The F.B.I. said in the 142 pages of documents that it had informants close to the Nation of Islam who let them know the details of Ali’s involvement with the group. That involvement first came into full view right after Ali first won the heavyweight title, by beating Sonny Liston in 1964.

It was then that Ali affirmed he was a member of the group and that he would no longer be known as Cassius Clay but as Muhammad Ali.

Years later, Ali converted to orthodox Islam. But in 1966 the F.B.I. focus was on the Nation of Islam, which a hodgepodge of agency documents refer to as an “all-Negro, semireligious, antiwhite” organization. The records, which refer to Ali as Clay, show that the bureau was paying particularly close attention to the group’s leader, Elijah Muhammad.