A British gallery says a restoration project for Leonardo da Vinci's "Virgin of the Rocks" has revealed new details and suggest the artist may have painted all the picture himself, instead of with his assistants as previously thought.

The National Gallery says the 18-month project removed some yellowing varnish, enabling experts to take a closer look at the painting's brush strokes and styles.

It said Wednesday that research affirmed that the Renaissance artist likely painted the entire picture himself and intended for it to be unfinished....