DETROIT, May 18 — The Federal Bureau of Investigation, plenty experienced in searching for James R. Hoffa, said a "fairly credible lead" is what led investigators this week to still another potential burial spot: a horse farm aptly named Hidden Dreams.

Using cadaver dogs borrowed from the Detroit police, and aided by students and professors from Michigan State University, F.B.I. agents began a search on Wednesday of the 80-acre farm in Milford Township, Mich., northwest of Detroit, for signs of a crime involving Mr. Hoffa, the former Teamsters president. Daniel D. Roberts, the special agent in charge of the Detroit F.B.I. office, said the search could take weeks.

In fact, the search has taken more than 30 years, and has led investigators to trash dumps, construction sites and homes throughout the region. One theory even held that he was entombed under Giants Stadium at the Meadowlands in New Jersey.