ELMIRA, N.Y. -- Police are investigating the theft of a bronze plaque from a monument at Mark Twain's gravesite in upstate New York.

The superintendent of Woodlawn Cemetery in Elmira said Monday the 30-by-30-centimetre likeness of the American writer was likely stolen between Christmas and New Year's Day.

The plaque showing Twain's image was one of two on a 3.6-meter 78-year-old granite monument commissioned by Twain's daughter Clara. The other plaque, of Clara's husband, was untouched.

Twain was born Samuel Langhorne Clemens and grew up in Hannibal, Missouri.

The author of such classics as "The Adventures of Huckleberry Finn" and "Tom Sawyer" married Olivia Langdon of Elmira and had a summer home in the upstate city. He died in 1910 and was buried in the Langdon family plot at Woodlawn.