Scientists have determined that a carcass found on a beach on Massachusetts' Nantucket island is a great white shark.

State Energy and Environmental Affairs spokeswoman Lisa Capone says shark experts hadn't seen another great white wash up on a Massachusetts beach in at least two decades.

The 6 1/2-foot-long young female shark was discovered Monday.

An expert from the state's Division of Marine Fisheries examined the shark Tuesday.

Lifeguards at a Martha's Vineyard beach reported a possible sighting of a great white shark last week.