Tipster remains certain Hoffa buried in Detroit suburb

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. By Hank Winchester, Shawn Ley and M. Alex Johnson, NBC News Police in Roseville, Mich., were awaiting lab reports Tuesday to determine whether there are human remains under a shed where a tipster says the body of former Teamsters President Jimmy Hoffa was buried 37 years ago. Hank Winchester and Shawn Ley are reporters for NBC station WDIV of Detroit. M. Alex Johnson is reporter for NBC News. Follow him on Twitter and Facebook. Scientists at Michigan State University had been scheduled to issue their report Monday on two soil samples taken from a home in Roseville, a suburb of Detroit, after the unidentified tipster told authorities that he witnessed a body being buried there the day after Hoffa disappeared in July 1975. Late in the afternoon, police said the results wouldn't be available until Tuesday. The lab tests are only a preliminary step to help determine whether anyone is buried on the property. Were they to come back positive for human remains, authorities would then have to dig them up before further tests could be conducted to figure out whether they were indeed those of Hoffa. The disappearance of Hoffa — who ran the International Brotherhood of Teamsters, the country's biggest labor union, from 1957 to 1971 — has long fueled conspiracy theories. Watch US News videos on NBCNews.com Investigators and other experts have said they are doubtful that Hoffa will finally have been found. 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, said he "never thought that Hoffa was here, ever." But the unidentified police informant is "100 percent convinced" that Hoffa's body is buried there, said Moldea, who told NBC station WDIV-TV of Detroit that he had been in "constant contact" with the man. "'Well, if they don't find anything, they have to dig up the driveway,'" Moldea quoted the man as having said. Police continued to guard the home Tuesday in Roseville, where national media and curious onlookers have gathered since the story made international news last week. The current owner of the home, Pat Szpunar, described the scene as "three-ring circus." The attention has frightened the tipster, who fears that organized crime groups might come after him for talking, Moldea said, who said that was a legitimate concern. "He's so frightened," Moldea said. "One of the people who is involved in this is still alive, has teeth. He can still bite." Moldea didn't identify that person. More content from NBCNews.com: A week later, search still on for 73-year-old accused of killing daughter-in-law Video: Like hurricanes, winter storms to get names too Cell phone video shows cop striking woman after Philadelphia parade State Dept: Missing American journalist Austin Tice believed held by Syria regime NYPD commissioner blames rise in crime rate on Apple thefts Follow US News from NBCNews.com on Twitter and Facebook