The case closely echoes the removal of another terra-cotta wine vessel, the Euphronios Krater, from the museum in 2008 after evidence surfaced that it had been illegally excavated from an ancient burial ground in Italy. Met officials said they believe, as do law enforcement officials, that both vessels went through the hands of Giacomo Medici, a 79-year-old Italian art dealer who was arrested in 1997 and convicted in 2004 of conspiracy to traffic in antiquities.

Mr. Medici, reached in Italy, denied any role in connection with the recently seized vase, which the Met bought at auction at Sotheby’s in 1989 for $90,000. An official for the auction house declined to identify the consignor, citing privacy concerns, but said Sotheby’s had no knowledge of any issues with its provenance when it handled the sale.

Experts date the vase, which is also known as a bell krater, to 360 B.C. and attribute it to the Greek artist Python, considered one of the two greatest vase painters of his day.

While its significance does not rise to the level of the far larger Euphronios Krater, which the Met sent back to Italy after a 30-year dispute, the newly confiscated vessel is a remarkably intact survivor of an age when the Greeks colonized Paestum, a Mediterranean city in the Campania region south of Rome, and created temples and artworks of legendary beauty.

The forensic archaeologist who tracked the Python vase, Christos Tsirogiannis, a lecturer with the Association for Research Into Crimes Against Art, published his suspicions about the antiquity in The Journal of Art Crime in 2014 and said he sent his evidence to the Met then as well.