Oakland County Deputy Prosecutor Jim Halushka confirmed that investigators ripped up floor boards for more analysis after a cable news network determined there were traces of blood in the Detroit house. The network sent a forensic team to the house in late March.
According to a soon-to-be released book by Charles Brandt, former Pennsylvania Teamster official Frank Sheeran admitted to shooting Hoffa inside the home in 1975. Sheeran died Dec. 14 in a nursing home near Philadelphia.
Hoffa disappeared from an Oakland County restaurant parking lot on July 30, 1975. At the time he vanished, Hoffa, who took charge of the Teamsters in 1957, was on his way to a meeting with Anthony Provenzano, a New Jersey Teamsters boss, and Anthony Giacalone, a Detroit Mafia captain.
Investigators believe Provenzano and Giacalone had Hoffa killed to prevent him from regaining the union presidency after he served time in federal prison for jury tampering.
Theories about where he is buried are varied and include reports he is entombed under Giants Stadium.
In March 2002 the FBI referred the case to the Oakland County Prosecutor's Office for possible state charges, saying the federal case was stymied because of the length of time since Hoffa disappeared.
Last July, authorities, in what proved to be a false lead, dug up a backyard swimming pool in Bay County's Hampton Township in search of information that could shed light on Hoffa's fate.