A beachgoer found the carcass and reported it to lifeguards.

"They are not sure if it was a newborn or whether it was a yearling, but it was very young," said Wende Goo, a spokeswoman with the National Oceanic and Atmospheric Administration's National Marine Fisheries Service.

The carcass will be flown today to California for a necropsy, she said.

The young whale belonged to a pod of about 200 melon-headed whales that arrived Saturday.

The whales usually stay far from shore, so it was a mystery as to why they came into the bay, according to Brad Ryon, a marine biologist with NOAA.

The whales, which look and act like dolphins, swam about 100 yards offshore and didn't appear to be in distress, lifeguards reported Saturday.

A team of NOAA veterinarians and marine biologists and specialists from the Hawaiian Islands Stranding Response Group arrived at the bay Saturday night.

Volunteers camped on the beach overnight to ensure no whales beached themselves. On Sunday, they paddled outrigger canoes to help coax the whales out to sea. They towed a rope of vines between their canoes to move the whales, Goo said.

"It wasn't anything that was thrashing," she said. "Someone described it as a very spiritual event."

It has been about 30 years since there was another mass sighting of melon-headed whales close to shore, Ryon said. About 30 whales were found stranded on the beach in Hilo Harbor.

Ryon was looking into the possibility that the Rim of the Pacific military exercises may have had something to do with the whales' behavior. Six ships northwest of Kaua'i ceased sonar operations as a precaution Saturday, a RIMPAC spokesman said.

Melon-headed whales, which grow to about 9 feet and weigh 370 to 400 pounds, usually swim at least 20 miles offshore. Pods usually range from 100 to 500, with a maximum of about 2,000.

Two melon-headed whales beached themselves and died last August at Hau'ula Beach Park.