About 40 pilot whales have become stranded on a Cape Cod beach less than a day after volunteers pushed them back out to sea from another beach.
The development is being taken as bad news and may be a sign the whales are dying, an expert said.
The small black whales, which had been tagged on Monday before being freed from Chapin Beach in Dennis, have been found stuck in shallow water 25 miles to the east.
About 20 people are at the remote beach in Eastham are trying to keep the whales wet until they can be returned to deeper water again.
Chris Bailey, of the International Fund for Animal Welfare, said blood samples may be taken to determine if they are ill, in which case the whales might need to be euthanised.
"This is pretty bad news for them considering they've refloated once," said Kristin Patchett, of the Cape Cod Stranding Network. "The fact that they've stranded again probably means they're in pretty bad shape. It's not a very good day, unfortunately."
Kristin Patchett said the pilot whales go into shock when they strand, and if that can't be reversed, they will wind up stranding again or dying at sea.