Soil samples taken from the back garden of a Detroit house show no traces that former Teamsters union boss Jimmy Hoffa, or anyone else, was buried there, police have said.
Police decided to search the suburban property in Roseville after a tip-off from a man who claimed he saw someone being buried there about 35 years ago.
Mr Hoffa was last seen on July 30, 1975, outside an Oakland restaurant where he had been due to meet a New Jersey Teamsters boss and a Detroit Mafia captain.
His body has never been found despite a number of searches over the years.
In a statement, Roseville police said: "Our department just received the soil sample report from Michigan State University, after a battery of tests; the samples submitted for examination showed no signs of human decomposition.
"As a result of these tests the Roseville Police Department will be concluding their investigation into the possible interment of a human body upon the property."
The soil samples were removed on Friday after officials drilled through the floor of a shed behind Patricia Szpunar's home. Police had said the ground would be excavated if decomposition had been found in the samples.
Ms Szupnar said she was now glad to have her shed back.
"The police have left and the yellow tape has come down," she said.
"I'm thrilled because it's over with. No more people staring at my house, driving by, walking by, pausing to stare. I can go on with my life.
"My son can put the motorcycle back in there."
A number of theories about the demise of Mr Hoffa have surfaced over the years.
Some say he was entombed in concrete at Giants Stadium in New Jersey, others that his body was ground up and thrown into a Florida swamp or obliterated in a mob-owned fat-rendering plant.