Twelve dolphins have died off eastern Long Island, and boaters were searching for any others still trapped in the shallow waters, a rescue leader said Sunday.

Rescue workers gather around a Marine Research and Preservation van at Northwest Creek cove in East Hampton, New York, 16 Januar 2006. Rescue workers gather around a Marine Research and Preservation van at Northwest Creek cove in East Hampton, New York, 16 Januar 2006. [AFP]

Chuck Bowman, president of the Riverhead Foundation for Marine Research and Preservation, said two of the animals died overnight and were discovered at dawn Sunday. Necropsies were being performed on the dead animals to learn why they died, he said.

Eight of the approximately 20 "common dolphins" swam to safety after they were first spotted about 11 days ago in a cove north of East Hampton. With 12 dead, there may be no others trapped, Bowman said.

Rescuers were searching the area Sunday to make sure, he said.

"Common dolphins" and another type, "white-sided" dolphins, are found throughout the year in waters off Long Island and into New England. Typically, they stay 30 to 80 miles off shore.

This group may have been chasing bait food, such as mackerel, that came closer to the coast. A preliminary study of two of the dead dolphins found their stomachs were empty.