Updated

Authorities dug under a backyard pool in a residential neighborhood Wednesday in search of clues to the disappearance of ex-Teamsters boss Jimmy Hoffa (search) but came up empty after an eight-hour search.

Nearly 28 years after Hoffa disappeared from the Detroit area, law enforcement officials combed the site where an informant said a briefcase was buried that contained a syringe and possible evidence that Hoffa had been injected with drugs or poison.

When nothing was found, the search was ended, said Jeffrey Werner, chief of the Bloomfield Township Police, the lead investigative agency in the case.

"We thought this information was pretty good, and that's why we went to all this effort and we're frankly disappointed that we didn't find something," he said.

Hoffa, 62, vanished the afternoon of July 30, 1975, from a parking lot in Oakland County, about 25 miles north of Detroit. Hampton Township is a few miles northeast of Bay City, about 100 miles away.

Authorities said the informant, an inmate named Richard Powell who is imprisoned for killing his landlady in 1982, led a team to the spot. He lived in the home in the 1970s.

Bay County Undersheriff Joel Luethjohann said Powell told investigators in March that he buried the body of a missing Bay City man in the crawl space beneath the same home.

Acting on that information, state police investigators found the body of Robert A. Woods, who had been missing for nearly 30 years.

Powell had long claimed a role in the Hoffa case, but authorities had not taken him seriously.

He told The Bay City Times in a 1984 prison interview that in the 1970s he was involved with gangsters in an auto theft ring and was assigned to drive a motor home containing a body to northern Michigan. He said someone else supposedly came to dispose of the body, which was wrapped in a rug.

Powell changed the story earlier this year, telling officers that Hoffa's body was buried at his former home, where the aboveground pool now sits. Authorities decided to follow up on the lead in part because Powell's claim about Woods' body had proven true.

At the time he vanished, Hoffa was on his way to a meeting with Anthony Provenzano (search), a New Jersey Teamsters (search) 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.

Hoffa took charge of the Teamsters in 1957. He earned the loyalty of his members with contracts that improved their standard of living dramatically. It was under Hoffa that the Teamsters won their first national trucking contract.

He also earned the enmity of Robert F. Kennedy (search), who accused him of corruption and mob connections, first as counsel to a congressional committee investigating the unions, then as attorney general in his brother's Cabinet.

In 1967, Hoffa went to jail, sentenced to 13 years for jury tampering and fraud, but he refused to give up the Teamsters presidency. After he quit the job in 1971, then-President Nixon (search) pardoned him, and he began agitating to get his job back.

Hoffa's son James Jr. is now the Teamsters president. Teamsters spokesman Bret Caldwell said he planned no statement on the search.