NEW ORLEANS — A businessman pleaded guilty Wednesday to plotting to bribe an unidentified former New Orleans public official in a case that appears to be linked to a federal probe of former Mayor Ray Nagin.

Rodney Williams, who was president of Three Fold Consultants LLC, made $72,250 in payoffs to the unidentified official for his help in securing city contracts for architectural, engineering and services work, according to a court filing accompanying his guilty plea.

Williams made the first payoff in January 2008 in the form of three checks that totaled $60,000 and were made payable to a granite installation company operated by the official, the filing says.

Court records don’t name the city official, but his tenure matches Nagin’s two terms in office. Also, Nagin and his two sons owned a granite installation company that had a contract to install countertops for local Home Depot stores after Hurricane Katrina struck in 2005.

Nagin has not been charged. His attorney, Robert Jenkins, didn’t immediately respond to a call seeking comment.

Ralph Capitelli, one of Williams’ attorneys, wouldn’t name “Public Official A” listed in court papers.

“It would be the worst investigative reporter on the planet who couldn’t figure out who ‘Public Official A’ is,” Capitelli told reporters after the hearing.

Williams, 47, isn’t the first person to admit guilt in the probe. Businessman Frank Fradella pleaded guilty in June to making a $50,000 payoff to an unidentified former city official whose tenure also matched Nagin’s. Prosecutors said Fradella provided truckloads of free granite to the official.

In February, people with direct knowledge said federal authorities were investigating questions about free trips and gratuities that Nagin allegedly accepted while in office. They spoke on condition of anonymity because they could not publicly comment on an ongoing investigation.

The conspiracy charge to which Williams pleaded guilty carries a maximum sentence of five years in prison, but his plea agreement calls for a prison sentence ranging from 30 to 37 months. His sentencing is set for March 27. Williams can withdraw his guilty plea if U.S. District Judge Susie Morgan sentences him to more than 37 months.

Williams didn’t respond to reporters’ questions as he left the courthouse. Capitelli said his client “fully accepts responsibility for what he did” and is cooperating with federal authorities.

Williams received a “large number” of city contracts after the unnamed official approved him as a vendor for the city’s public works department in 2008, according to Wednesday’s court filing. After one of those contracts was awarded to Three Fold in July 2009, Williams delivered a $10,000 cash payoff to “close family members” of the official, the filing says.

To disguise the payments, the official allegedly provided Williams with ownership documents in his granite installation company. The documents made it appear the official sold a partial interest in his company to a company that Williams partially owned but wasn’t created until after the $60,000 payoff in January 2008.