For 15 years, some of the art world’s most established dealers and experts rhapsodized about dozens of newly discovered masterworks by titans of Modernism. Elite buyers paid up to $17 million to own just one of these canvases, said to have been created by the hands of artists like Jackson Pollock, Willem de Kooning, Mark Rothko, Franz Kline and Robert Motherwell.

But federal prosecutors say that most, if not all, of the 63 ballyhooed works — which fetched more than $80 million in sales — were painted in a home and garage in Queens by one unusually talented but unknown artist who was paid only a few thousand dollars apiece for his handiworks.

Authorities did not name or charge the painter and provided few identifying details except to say he had trained at a Manhattan art school in a variety of disciplines including painting, drawing and lithography. He was selling his work on the streets of New York in the early 1990s, they said, when he was spotted by a Chelsea art dealer who helped convert his work into one of the most audacious art frauds in recent memory.

The new details about the man said to have created the fakes were contained in a superseding indictment, handed up Wednesday against one of the co-conspirators, Glafira Rosales, an obscure dealer from Long Island who was arrested after a lengthy Federal Bureau of Investigation inquiry. She has been charged with wire fraud and money laundering in connection to what authorities have called a scam, but her boyfriend, alleged to be the other co-conspirator who discovered the painter, has not been charged.