A U.S. district judge refused to order the release of an affidavit the FBI used to get a search warrant to dig for Jimmy Hoffa's remains at a southeastern Michigan horse farm.

"Granting public access to sensitive information in a sealed affidavit would not play a significant, positive role in the investigation," Judge Marianne Battani wrote Monday in response to a request by the Detroit Free Press to release the document.

Battani said the affidavit included "the details of a threat made to a witness" and other information that should not become public.

The FBI spent two weeks last month searching the Hidden Dreams Farm, 30 miles northwest of Detroit in Oakland County's Milford Township. Officials said they found no evidence of Hoffa's remains.

The former Teamsters union president was last seen July 30, 1975, the day he was supposed to meet a New Jersey Teamsters boss and a Detroit Mafia captain at a restaurant about 20 miles from the farm. Both of those men are now dead.

The newspaper had argued that the estimated $250,000 cost of the search gave the public an interest in the contents of the affidavit.

"Judge Battani didn't engage in a critical analysis of the government's claims," said Free Press lawyer Herschel Fink. He said editors would decide whether to appeal.