A marble hand has been stolen from an ancient Greek relief at the British Museum, the museum acknowledged Saturday.

The theft - which happened in November but only became public on Friday - was probably vandalism or a prank, said Andrew Hamilton, a spokesman for the museum. The museum will review its security measures, he added. Hamilton said the hand is worthless separated from the relief, part of a 2,400-year-old panel from the Temple of Apollo in Bassae, in western Greece. The relief was found in temple ruins and brought to the British Museum in 1814, with the hand missing. A curator found the long-detached piece in a separate part of the museum collection in 1990, and it had been attached with a metal rod to the relief. News of the theft prompted anger in Greece, which has long sought the return of the so-called Elgin Marbles, carved figures and reliefs taken from the Acropolis in Athens by Lord Elgin, the British ambassador to the Ottoman Empire, in the early 19th century. Britain's refusal to return the pieces, which are known in Greece as the Parthenon marbles and are among the greatest treasures of Western art, is a sticking point in its relations with Greece.