In their decade-long investigation of the illicit antiquities trade, Italian authorities have amassed the strongest evidence to date that the most prized ancient Greek vase in New York's Metropolitan Museum of Art was looted.

The Euphronios krater, described as one of the finest antiquities ever obtained by the Met, has been a source of controversy since the museum acquired it 33 years ago.

Italian authorities have long maintained that the vase was looted from a tomb north of Rome, but the Met has refused to return it, saying the Italians lack "irrefutable proof."

Italians prosecutors now believe they have it, according to previously undisclosed court records obtained by The Times.

The records include excerpts from the handwritten memoir of Robert E. Hecht Jr., the American dealer who sold the krater, a terracotta bowl, to the Met in 1972. At the time, he told museum officials that he had acquired it from a Lebanese man whose family purchased it well before a 1939 Italian law prohibited the unauthorized export of antiquities.

But in his memoir, seized during a raid of his Paris apartment in 2001, Hecht tells a very different story. Instead of buying the krater from a reputable dealer with a documented ownership history, he says he purchased it in 1971 from an Italian dealer, Giacomo Medici, who was convicted last year of trafficking in looted art.

Medici turned up one morning at Hecht's apartment in Rome and showed him a Polaroid photograph of a krater signed by Euphronios, a master vase painter of ancient Greece, the memoir says.

Within an hour, Hecht writes, the two men flew to Milan and caught a train north to Lugano, Switzerland, where Medici had the bowl in a safe-deposit box. Hecht says he offered Medici 1.5 million Swiss francs — about $380,000 at the time — for the krater on the spot, making a cash down payment of about $40,000. He then headed straight to Zurich, he writes, where he left the krater with a restorer before heading back to Rome to go on a family ski trip.

In this account, he makes no reference to documentation establishing that the object had been legally excavated and exported from Italy.

Thomas Hoving, who acquired the krater when he was the Met's director, said Thursday in an interview that Hecht's memoir is "a very important piece of evidence."

"It proves, as the final nail in the coffin, where it came from," Hoving said.

Hecht said Thursday that this version from his memoir involving Medici was a fiction. Medici, in a recent interview in Rome, also denied the account.

The Italians' new evidence about the krater's origins emerges at a time of heightened controversy over the ethics of antiquities acquisitions, with Italy, Greece and other source countries pressing claims for the return of rare items they say were illegally removed.

Hecht and Marion True, the J. Paul Getty Museum's former antiquities curator, are now facing trial in Rome for allegedly trafficking in looted art. Medici was convicted last year in the same case and is appealing a 10-year prison sentence. Italy is also demanding the return of 42 objects from the Getty.

Among the other new evidence cited by the Italians is a sworn deposition by True before an Italian prosecutor. In the document, also obtained by The Times, she said Met antiquities curator Dietrich von Bothmer showed her an aerial photograph and pointed to the exact tomb in a heavily looted necropolis north of Rome where the krater had been excavated.

The Italians say Von Bothmer could not possibly have learned this from Hecht's Lebanese dealer, who said he had inherited the vase from his father and did not know where it was originally found. Von Bothmer denies True's account.

Additionally, Italian officials said in recent interviews in Rome that two men from Cerveteri, site of the ancient necropolis, have told them that they helped illegally remove the krater from a tomb in 1971.

Finally, the Italians say in court records that they have photographs of Hecht and Medici posing next to the vase at the Met. Medici, the records say, has traveled the world, posing next to objects he has sold to major museums.

Toward the end of Hecht's memoir, he briefly restates the official version of how he acquired the Euphronios Krater from the Lebanese dealer, the court records show.

But Italian authorities dismiss this version in court records as "a story told to hinder penal and civil actions in Italy," citing contradictions in the account.

On the basis of this new evidence, Italian authorities have renewed their demands for the return of the 2,500-year-old krater.

Used for mixing water and wine, the bowl portrays the death of Sarpedon, a son of Zeus, in a rarely depicted scene from Homer's "Iliad." It is considered one of the finest Greek vases to have survived antiquity. Only about two dozen kraters painted by Euphronios have survived, and experts say this is among the best preserved and most beautiful.

Today the krater is displayed in a first-floor gallery off the main corridor of the Met's Greek and Roman wing among dozens of other Greek vases.

The museum refused to comment on Hecht's memoirs. In a statement, the museum said that in February, it requested a meeting with the Italian Ministry of Culture for a "full discussion of works in the Metropolitan's collection that were the subject of the ministry's concern."

"The Metropolitan has reiterated its request for a meeting on several occasions this summer, and looks forward to such a discussion," the statement said.

Acquisition of the krater in 1972 sparked a media frenzy and judicial investigations in both the United States and Italy. But the Met has clung to Hecht's official story for decades.

Hoving called the piece "one of the two or three finest works of art ever gained by the museum."

But he later changed camps and called it "a hot pot," writing in a 1993 memoir about his stewardship of the museum that he was convinced it had been looted from Italy and that Hecht had duped the museum with the story of the Lebanese dealer.

Italian officials acknowledge that the statute of limitations has expired on possible civil and criminal claims that could have been used in the 1970s to repatriate the krater. They say the new case they are mounting is largely a moral one.

But they also note that substantial evidence implicating other antiquities at the Met has emerged in their investigation, and they suggest that criminal cases targeting the Met and other American museums may be in the works.

Hecht, reached by phone at his New York apartment, said of the two versions in his memoir, "One is the fact and the other is a fancy invention."

When pressed, he said the story of the Lebanese dealer was the truth and that he wrote the other version in the hope of selling more copies of the memoir, which he wanted to have published.

In a lengthy interview with The Times, Medici denied having anything to do with the Euphronios krater and cast doubt on the account in Hecht's memoir, saying Hecht got Medici's age wrong at one point in the account. He also provided The Times with photographs of him in front of the krater and other famous antiquities and paintings, saying it was his practice to take pictures in front of beautiful art — not just objects he bought or sold.

The material in Hecht's journals is only the latest evidence suggesting that the Euphronios krater was the product of illicit excavations.

Days after the acquisition, experts called Hecht's story of the Lebanese dealer suspicious. It led to inquiries by legal authorities in the United States and Italy.

In the mid-1970s, the Italian government pursued an unsuccessful criminal case against Hecht. A grand jury was convened in New York to investigate the transaction involving Hecht, Hoving and Von Bothmer. The grand jury found insufficient evidence for an indictment.