Six paintings thought to be by Jackson Pollock will be re-examined after tests suggested they were fake, the Pollock-Krasner Foundation has said.
Ed Harris played Jackson Pollock in biographical movie Pollock
University of Oregon analysis found "significant differences" between geometric patterns in the six paintings and previous Pollock works.
The six were among 32 paintings found on Long Island last year.
Foundation head Charles Bergman said investigation would continue until the paintings' authenticity was determined.
Signature 'not found'
A team led by physics professor Richard Taylor has analysed Pollock's work for the past decade, applying their findings to six of the 32 newly-discovered works.
They use a technique known as fractal analysis, which looks for geometric patterns that recur in the paintings despite the apparent chaos of Pollock's famed "drip" paintings.
"All of Jackson Pollock's poured paintings analysed by my research group are composed of a highly specific and identifiable form of fractal patterning," Professor Taylor wrote in his report, published in science journal Nature.
"Pollock's specific fractal signature has not been found in the submitted paintings," he added.
"The analysis has also revealed that the patterns vary between the paintings, indicating that they may have been painted by different hands."
The Pollock-Krasner Foundation, founded by Pollock's widow Lee Krasner to award grants to artists, praised Professor Taylor's "valuable contribution".
It commissioned his team to conduct further tests on six of the paintings.
The 32 paintings tested were unveiled by film-maker Alex Matter last May, who said he found the paintings among the possessions of his late parents, who knew Pollock.
Art historian Francis O'Connor, who is leading the foundation's investigation, said Professor Taylor's results "reinforce my own scepticism and reservations concerning the paintings".
However fellow art historian Ellen Landau said last year that she believed the newly-discovered paintings were authentic.
"Fractal analysis is still a very new and contested field in art authentication," Ms Landau said on Thursday.
"To the naked eye of experts, it is immediately evident that some of these experimental works do not look like standard Pollocks.
"What makes these paintings so compelling is their 'experimental' quality."