MIAMI — More than 80 false killer whales have been found dead after stranding themselves along the remote coast of Southwest Florida in Everglades National Park, the National Oceanic and Atmospheric Administration reported Monday.

So far, the death toll is 81, with just one of the rare whales found alive. Crews continue to search for another dozen or so from a pod originally thought to number about 100. It is the largest recorded stranding of such whales in Florida, officials said.

NOAA’s mammal stranding network first received a report of the beached whales near Hog Key on Saturday. Hog Key sits amid a dense network of islands off Southwest Florida, about 10 to 12 miles south of Pavilion Key, a popular camping site along the Wilderness Waterway in Everglades National Park.

After the U.S. Coast Guard confirmed the stranding, a team from NOAA and the Florida Fish and Wildlife Conservation Commission hurried to the scene, about an hour’s boat ride from shore, and tried to herd some of the whales to deeper water as daylight faded, said Blair Mase, the stranding network coordinator. They returned on Sunday and tried again, but were hampered by the shallow muddy flats and a shoreline tangled with mangroves.

The whales, which included adults, juveniles and calves, were “deeply embedded in some of the mangroves, making response efforts extremely difficult,” Mase said.

Lack of cellphone service also complicated the rescue attempt, she said. The crews also had to deal with sharks.

Rescuers ended up euthanizing nine of the whales too sick to survive, Mase said. Another 72 died on their own by Sunday. Monday morning, a live whale was spotted, which the team is continuing to search for.

Park officials have closed the area around the key and are asking boaters and planes to steer clear as a dozen organizations, including the U.S. Coast Guard and Mote Marine Laboratory, assist in the search.

False killer whales are a type of dolphin and closely resemble killer whales without the white patches. Males can grow up to 20 feet. Strandings in the U.S. happen rarely: the last occurred in 1986 when a pod of 40 swam close to Cedar Key, but only three stranded themselves, Mase said. In 1980, 28 whales stranded off Key West. The largest stranding on record occurred in 1946 in Argentina, when 835 whales beached themselves.

“We consider this a rare occurrence,” Mase said.

Little is known about the whales in the wild. In the early 1990s, according to a 2012 assessment, nearly 400 were counted in the northern Gulf of Mexico. But because the data is old, the report concluded that too little information is available to determine the whale’s status off Florida shores. They typically swim in the open ocean, prefer warm water, are believed to live to about 60 and form strong social bonds, swimming in pods of 10 to 20.

Wildlife officials are still trying to determine what caused the whales to strand, Mase said, and have collected samples from the dead whales.