FORT PIERCE, Fla. -- More than 20 pilot whales came ashore on a South Florida beach on Saturday, triggering a daylong effort by state and national officials, nearby residents and others to save them.

By evening, five pilot whales - two calves and three juveniles - had been transported to Florida Atlantic University's Harbor Branch Institute for rehabilitation. The rest had died of natural causes or had to be humanely euthanized, said Allison Garrett, a spokeswoman for the National Oceanic and Atmospheric Administration's fisheries service.

UPDATE: Get the latest on the whales here.

"It was not possible to rehabilitate them," she told the Associated Press.

The pod of 22 whales came ashore Saturday morning at Avalon Beach State Park in St. Lucie County. They ranged from calves and juveniles to adult whales.

Garrett said it was unclear why the whales became stranded.

"Pilot whales are very social animals," she added. "One scenario could be one of the animals was sick. They won't leave (a sick whale). They'll stay together."

For this reason, it's useless to push pilot whales back into the ocean, Blair Mase, stranding coordinator for NOAA's Southeast Region, told TCPalm.com ( ). http://bit.ly/TJA0D2

"If you push them into the water, they'll just keep coming back and stranding themselves again," said Mase, who was surfing in the area when he noticed people running toward the beached whales.

TCPalm.com reports that hundreds of residents came to the beach to assist with the rescue, helping the animals turn upright so they could breathe better. Volunteers covered the whales with moist towels and poured water over them. Red Cross volunteers helped ensure that volunteers stayed hydrated in the hot sun.

"I think that people want to help animals," said Jacqui Thurlow-Lippisth, a Harbor Branch volunteer who worked with others to tend to juveniles in a shaded inflatable pool. "Especially whales and dolphins, because they are our counterparts in the seas. They're mammals, they're intelligent, they're social. They're a lot like us."

Still, there was a sad undercurrent to the efforts, with rescuers aware that most of the whales were dying.

Garrett said there was no obvious sign of trauma or injury to the whales, but that necropsies would be performed on them. She said officials and volunteers spent the day assessing the health of the whales to see which could be rehabilitated, and then making the others comfortable.

She said the last such beaching in the area came in May 2011, on the Florida Keys.

___

Associated Press writers Kelli Kennedy in Miami and Norman Gomlak in Atlanta contributed to this report.

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