FORT PIERCE, Fla. -

Rescuers continue to work to save four surviving juvenile whales that beached in a pod of 22 Saturday morning.

The pod of short-finned pilot whales washed up at Avalon Beach State Park near Ft. Pierce. Volunteers worked with rescuers to save the group of whales, but 17 died.

SeaWorld veterinarians said one of the five surviving whales died Monday afternoon, bringing the total of dead whales to 18.

Officials from the Fish and Wildlife Conservation Commission  said it's unclear why the whales became stranded. Experts will conduct necropsies to determine the cause.

TCPalm reports there were at least four calves in the stranded pod and officials said they have the best chance at survival.

Hundreds of residents came to the beach to assist with the rescue, helping the animals turn upright so they can breathe better and pouring water over them.

SeaWorld veterinarians are working to evaluate the 4 surviving whales, which are being held at the Harbor Branch Oceanographic Institute in Ft. Pierce. Officials with SeaWorld say if the whales make it they'll be transported to SeaWorld's care facility in Orlando.

Whale experts will make sure it's safe to transport the whales, but there is no firm timeline on if or when they'll make the trip.