The FBI and the Isabella Stewart Gardner Museum ­received a flood of tips from around the country Tuesday, as new details emerged about the turning point in the investigation of the notorious Gardner Museum heist 23 years ago.

The latest, exhaustive phase in the inquiry is based on a tip that a caller made to authorities in 2010, according to Anthony Amore, the Gardner Museum’s head of security and chief investigator.

He said Tuesday that the tip was so fruitful — leading to the announcement that investigators know the identities of the thieves and could trace the art from Boston to Connecticut and Philadelphia — that the FBI has since rededicated significant resources to investigating the heist.

“That tip, plus thousands of man-hours, led to where we are today,” Amore said.

The US attorney’s office in Boston — which earlier this week joined the FBI in saying publicly for the first time that they know the identity of the thieves, although not the current location of the missing paintings — has assigned two prosecutors to the investigation, and they have communicated with investigators in ­Connecticut and Philadelphia.

“We really have reached a point in the investigation where the whodunit part is over, and now, ‘Where’s the art?’ ” Damon Katz, chief counsel for Boston’s FBI division, said Tuesday. “That’s the only thing we’re ­focused on in this point of this investigation; it’s finding the art with the public’s assistance.”

Investigators hope that a public awareness campaign they announced Monday — 25 billboards with images of the stolen art went up Monday in Philadelphia — will lead to further tips, in what has been called the final chapter of the investigation.

“I do believe there are people out there who can give us information that will get us to the paintings,” said Amore, who has worked closely with federal investigators.

He added, “Assistance from the public is essential.”

The public awareness effort, which includes a $5 million ­reward being offered by the museum for the return of the art in good condition, is similar to the campaign that ultimately led to the arrest in June 2011 of James “Whitey” Bulger after 16 years on the lam. With Bulger in custody, public officials have said that their focus has turned toward the Gardner heist, one of the greatest and most sophisticated art thefts in history.

“It’s been 23 years that those paintings have been missing from the museum, and we would like very much to put them back there,” said Katz.

Neither he nor Amore would discuss Tuesday the nature of the tips ­received.

The theft has captivated the public’s imagination in large part because of the boldness with which it was carried out. Two men dressed as Boston ­police officers conned their way into the museum in the early morning hours of March 18, 1990, telling the two guards on duty that they were responding to a disturbance.

They tied the guards up with duct tape, left them in a basement, and made their way through the museum, walking off with 13 artworks, including three Rembrandts, a Vermeer, and a Manet. The artworks were valued at $500 million, though they are essentially priceless in that they have ­become so legendary.

Authorities would not disclose the identities of the people they believe were involved in the heist, saying it would hinder the investigation, but the declaration that some of the works made their way through organized crime circles in ­Connecticut and Philadelphia has helped to confirm a line of inquiry that has emerged in ­recent years.

The latest focus has been on Robert Gentile, a 75-year-old ailing Mafia figure with ties to organized crime in Philadelphia and Boston. His Connecticut home was searched last year in relation to the heist. He was charged with drug dealing and possession of an illegal firearm in what his lawyer called a tactic by the FBI to pressure him to disclose information about the heist.

Gentile, who pleaded guilty and is slated to be sentenced in May, faces a lengthy prison term. His lawyer, Ryan McGuigan, has maintained that Gentile knows nothing about the heist or the whereabouts of the artwork.

But investigators seem to have trained their focus on Gentile in the recent phase of the investigation.