WESTPORT, Mass. (AP) — A Massachusetts marine biologist who examined a 13-foot great white shark carcass found ashore near the Rhode Island state line wasn't able to determine how the shark died, state officials said Sunday.

State biologist Greg Skomal performed a necropsy on the 1,500-pound male shark Saturday and found no signs of trauma. A fisherman discovered the carcass Saturday morning on a rocky shoreline in Westport, less than a half-mile from public beaches in Little Compton, R.I.

"They will have a difficult time, if at all, figuring out how he was killed," said Krista Selmi, a spokeswoman for the Massachusetts Division of Marine Fisheries.

Little Compton officials closed Goosewing and South Shore beaches after the shark was found. Both beaches reopened Sunday and police sent out a patrol boat to watch for other sharks.

Selmi said officials plan to leave the shark's body where it is.

"There's really no means to move an animal of that size," she said.

The shark appeared to have washed ashore Friday night, Selmi said. The carcass is below the high tide level, and officials hope the tide drags the shark back out to sea.

Shark sightings have been rare in the area. But further east, there have been numerous reports of sharks off Cape Cod. In July, a man was bitten on his legs by a great white shark while swimming off Ballston Beach in Truro, Mass.