More than 270 previously unknown works by Pablo Picasso recently came to light when a retired electrician sought to have them authenticated by the late artist's estate, the Picasso Administration said Monday.

But in a strange twist, 71-year-old Pierre Le Guennec finds himself slapped with a lawsuit filed by the artist's son, Claude Picasso, and five other heirs who say the works are stolen.

The lawsuit was first reported Monday by the French newspaper Liberation.

The works -- a collection of cubist collages, drawings, lithographs, notebooks and a watercolor -- were revealed in January when Le Guennec contacted the Picasso estate by mail to request certification of authenticity. Along with the letter, Le Guennec included 26 photographs of previously unpublished Picasso pieces....