Chicago ? FBI agents were always sure that 18 unsolved murders, some dating back more than three decades, were ordered by some of the top men in the Chicago mob. But they were never able to arrest anyone for the crimes — until now.

Before first light on Monday, government agents with arrest warrants in hand began knocking on the doors of major organized crime figures in the Chicago area, Florida and Arizona, following what federal officials described as the most far-reaching mob indictment in Chicago in decades.

Fourteen reputed mob figures, including two retired policemen, were indicted as a result of a racketeering case charging conspiracy to commit 18 murders dating as far back as 1970.

Those indicted included 63-year-old James Marcello, identified by FBI officials as the leader of organized crime in Chicago, and longtime mob leader Joey “The Clown” Lombardo, 75. Marcello was arrested, and a manhunt for Lombardo was under way in Chicago.

“The mob takes a hit today,” U.S. Atty. Patrick Fitzgerald told reporters in announcing the charges.

The murders included those of the Chicago mob’s one-time top man in Las Vegas, Anthony “The Ant” Spilotro, 48, and his brother, Michael, 41, whose badly beaten bodies were found in an Indiana cornfield in 1986. Joe Pesci played a character based on Tony Spilotro in the 1995 Martin Scorsese movie “Casino.”

The indictment — resulting from an investigation code-named Operation Family Secrets — alleges that 11 of the 14 defendants were involved in the murder conspiracy and that seven actually murdered someone or agreed to commit murder. The three remaining defendants were charged with other crimes.

Prosecutors said all of those charged were connected in some way to the Chicago mob, also known as the Chicago Outfit or the Chicago Syndicate. Among those charged were two retired police officers accused of informing one of the suspects about possible mob members who were helping federal investigators.

Authorities found all but two of the defendants — Lombardo and alleged mob enforcer Frank Schweihs, 75, of Dania Beach, Fla.

Another defendant, Frank Saladino, 59, was found dead Monday morning in a hotel room in Illinois when FBI agents went to arrest him. They said he appeared to have died of natural causes.

Two Indiana state troopers kneel at the edge of a grave where the bodies of reputed mobsters Anthony and Michael Spilotro were found, in this June 23, 1986, file photo from Enos, Ind. Fourteen reputed organized crime figures were indicted Monday on charges of plotting at least 18 murders, including those of the Spilotro brothers.