NANTES?A hitherto unknown music score by Wolfgang Amadeus Mozart has been discovered in library archives in a French city, the library announced Thursday.

The score, on just one page, had been known about for some time but was only authenticated by Austrian researchers last year, said the municipal Mediatheque library in the western city of Nantes.

It was part of the collection of Pierre-Antoine Laboucheroe, a 19th-century collector who donated his legacy to the city.

The partition was authenticated by a researcher from the Mozarteum Foundation, which is based in the composer's hometown of Salzburg in Austria.

The score was written on a sheet of paper just 10 centimeters (four inches). It appears to be a "credo in D major," and there is a second piece which looked like a "first draft, in parts illegible," said a library official.

Born in Salzburg in 1756, Mozart moved in 1781 to Vienna where he composed his most famous works.