NEW YORK – Yale University has found a treasure in a storage room underneath its art gallery: an oil painting it now attributes to 17th-century Spanish master Diego Velazquez.

“This is thrilling for us,” said Laurence Kanter, curator of European art at the Yale University Art Gallery, in a telephone interview. “This is one of the most important discoveries in the old-master field in decades.”

The unsigned painting, “The Education of the Virgin,” was originally credited to an unknown 17th-century Seville artist. Depicting the Virgin Mary and her mother, it was a gift in 1925 from two wealthy Yale alumni, Henry Hotchkiss Townshend and his brother Raynham Townshend.

In 2002, when the gallery was preparing for renovation and paintings were transferred to off-site storage, Kanter said the “Virgin” painting caught his eye for being of very high quality.

John Marciari, a Yale-educated art historian working for Kanter, said he too was struck by the long brush strokes, gesturing hands and sophisticated naturalism.

“One day it hit me,” he said. “It couldn’t have been more obvious. That’s early Velazquez.”

Marciari said he spent weeks trying to convince himself otherwise before he told anyone of his theory. Finally, he sent an image via e-mail to a Velazquez scholar he knew, Salvador Salort-Pons. There was a reply within a minute.

“I am trembling,” Salort-Pons wrote.

Years of academic and technical research followed.

“Technical study can disprove an attribution, but it can’t prove it,” said Marciari, who today is curator of European Art at the San Diego Museum of Art. “We did find the pigments and the canvas are all consistent with what Velazquez used when he was in Seville in the first years of his career.”

“I’ve spent seven years playing devil’s advocate, to convince myself it’s by someone else,” he said. “I feel certain it’s by Velazquez.”

The painting, dated 1617, has been damaged by water. Kanter said it will be ready for public viewing in about two years.