ALEXANDRIA, Virginia (AP) ― A federal judge will seek to unravel an art mystery and determine the rightful owner of a napkin-sized painting by French impressionist Pierre-Auguste Renoir that a Virginia woman says she bought at a flea market for $7.

The ownership is in dispute after documents were uncovered showing a Baltimore museum reported the painting stolen more than 60 years ago.

The painting has been seized by the FBI, and the federal government filed an action last month in U.S. District Court in Alexandria asking a judge to determine who should keep the painting.

Among the contenders is Marcia “Martha’’ Fuqua who has told the FBI that she bought the painting at a flea market in late 2009 for $7 and stored it in a plastic trash bag for two years before having it authenticated as a genuine Renoir.

Last year, Fuqua planned to have the painting sold at auction, where it was expected to fetch at least $75,000. But the auction was postponed after it was learned that the Baltimore Museum of Art reported the painting stolen in 1951. Records show an insurer, the Fireman’s Fund, paid a $2,500 claim on the theft.

The insurer says it is now the rightful owner, based on payment of that claim.

According to an appraisal commissioned by the FBI, Renoir painted “Paysage bords de Seine,’’ or On the Shore of the Seine, on a linen napkin in 1879 on the spot at a riverside restaurant for his mistress.

The appraiser says the Renoir’s value is about $22,000, much less than the auction house estimated, because Renoir’s paintings have fallen out of favor with some art collectors who consider them old fashioned and because questions about the painting’s ownership and possible theft diminish its value to collectors.

Fuqua, who had managed to remain anonymous until the court case was filed, told the FBI under penalty of perjury that she bought the painting at a flea market, never believing the painting to be a true Renoir, even though a plate reading “RENOIR’’ is attached to the frame. She describes herself as an “innocent buyer’’ and questions the FBI’s authority to seize the painting.