Jerry Siskind / AFP - Getty Images file

Jimmy Hoffa and his son, James P. Hoffa, who later also became president of the Teamsters, in a 1971 photo.

Updated at 3:40 p.m. ET: Soil tests indicate that no human remains are buried beneath a shed in Roseville, Mich., where authorities were investigating the possibility that the late Teamsters President Jimmy Hoffa might have been buried, officials said.

Scientists at Michigan State University tested two samples from a home in Roseville, a suburb of Detroit, after an unidentified tipster told authorities that he witnessed a body being buried there the day after Hoffa disappeared in July 1975. 

Those tests came up negative for human remains, Roseville police said Tuesday.

The lead appears to be yet another dead end in the search for Hoffa, who ran the International Brotherhood of Teamsters, the country's biggest labor union, from 1957 to 1971. It joins a long line of false leads that have fueled conspiracy theories for years.

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Investigators and other experts had said that they doubted that Hoffa was at the site.

Andy Arena, the former FBI special agent in charge for Detroit, said that while his "gut feeling is that this person saw something," it defies common sense to believe that the Mafia would have buried the body in broad daylight in a busy suburban area.

"If this guy was standing there watching this, and it was Jimmy Hoffa, he would have been in the hole with him," Arena said.

1976 FBI memo on Jimmy Hoffa's disappearance (.pdf)

Dan Moldea, author of "The Hoffa Wars" and numerous other books on organized crime, also said he "never thought that Hoffa was here, ever."

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Burbank Police Department via Reuters

Stephen Ivens is seen in this undated photograph provided by the Burbank Police Department.

A body found behind a church in Burbank, Calif. is that of missing FBI agent Stephen Ivens, police said on Tuesday.

Police found the body of the 35-year-old agent, who has been missing since early May.

Two hikers, who smelled a suspicious odor, discovered the body on Monday night behind a church on Scott Road in Burbank and reported it to police, said Burbank Police Department Sgt. Darin Ryburn.

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Ryburn said police have notified family members of the discovery and believe it's Ivens' body but are awaiting confirmation of the identity from the coroner’s department.

"Every indication is that it's Stephen Ivens," Ryburn said.

Ivens' boss at the FBI was at the scene as were other FBI colleagues. A weapon was recovered. Coroner's officials were working to confirm a cause of death.

Ryburn said it appears the body may have been at the location since Ivens went missing 67 days ago.

Ivens was last seen leaving his Burbank home on May 10.

An avid hiker, Ivens was thought to have ventured into the nearby hills after leaving home distraught.

NBCLosAngeles.com is operated by KNBC, NBC News' station in Southern California.

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