The reputed Mafia "soldier" arrested in the slaying of a witness in the investigation of Labor Secretary Raymond J. Donovan had ties to several of the organized-crime figures who had been involved in the inquiry, law enforcement sources said yesterday.

Salvatore Odierno, 66, being held without bail in last week's killing of Nat Masselli, was identified by the sources as a member of the Genovese family of the Mafia and a frequent visitor at a Bronx social club run by Joseph (Hooks) Verlezza.

In his June report on the Donovan investigation, special prosecutor Leon Silverman listed Verlezza as one of the organized-crime figures with whom Donovan was alleged by government informants to have had "a relationship."

Silverman had planned to call Verlezza before a federal grand jury in connection with reports that Donovan had met in Miami in January, 1979, with several reputed mobsters, including Nat Masselli's father, William.

Verlezza received a summons for a June appearance shortly before Silverman's report was issued but was excused from testifying "due to an injury from which he was recuperating."

Other law enforcement sources said Odierno was also an associate of Philip Buono, described in Silverman's report as a "made guy" in the Mafia who stood behind William Masselli.

The term "made guy" refers to someone sworn into the Mafia, or La Cosa Nostra, at a secret ritual centering on a blood oath to obey its rules and keep its secrets.

William Masselli, 55, another reputed "soldier" in the Genovese crime family, began working in the mid-1970s as a subcontractor for Donovan's firm, Schiavone Construction Co., on several New York City subway projects.

Masselli took over the work from Louis Nargi who told FBI investigators in 1980 that he fell into debt to Masselli and then lost "total control" of the business after a heated argument with Masselli.

"Nargi advised that the reason he 'walked away' from the business was because Masselli knows all sorts of dangerous people and that the risk was too great for him to object to Masselli's takeover of his business," the FBI reported.

"Nargi said that he . . . knew that Masselli was a friend of Philip Buono, whom Nargi knows as a 'made guy' in the Mafia. He also knew that to fight a 'made guy' meant danger to him since the word on the street is that 'made guys hurt people.' "

Buono was also summoned to appear before the grand jury in connection with the investigation of Donovan's activities in the Miami area in January, 1979. Donovan said in May through his lawyer that he stayed at his home in Boca Raton for about a week during that period but never saw Masselli.

Donovan has also denied any other links to organized-crime figures and said after being interviewed by Silverman Sunday that he is confident he will be cleared of the "newest allegations" under scrutiny.

Silverman had reopened his probe, sources say, partly because of fresh assertions about a 1979 meeting in the Miami area involving Donovan and Masselli and perhaps other gangland figures.

Odierno is being held by New York authorities on a charge of intentionally killing Nat Masselli, who was shot in the back of the head last Wednesday night shortly before his father was to be called before a grand jury under Silverman's supervision. Witnesses said two men jumped out of Nat Masselli's car after the shooting and got into a red Pontiac waiting nearby.

Bronx District Attorney Mario Merola said the car, registered to Odierno, was found late Monday in a motel parking lot in Brooklyn and was being checked yesterday. He said two other men are being sought.

Some investigators think Nat Masselli may have compromised himself in the Mafia's eyes during the first phase of the investigation last May when he helped FBI agents record his conversations with a lawyer for Schiavone Construction.

The lawyer wanted Nat to convey a message to his father, on the eve of a scheduled grand jury appearance, about the allegedly innocuous nature of a Schiavone document obtained by Silverman.

According to both Massellis, the document was not innocuous. William Masselli said it reflected a $20,000 kickback he had paid in 1979 to a Schiavone official in return for a $200,000 loan.

Silverman later described the lawyer's action as ill-advised but not criminal.