Local authorities on Wednesday said a beluga whale that became stranded in the Seine River in northern France died hours after it was taken from the waterway in a rescue effort.
"Despite an unprecedented rescue operation for the beluga, we are sad to announce the death of the cetacean," the Calvados prefecture tweeted.
Officials said the whale had to be euthanized after it developed breathing difficulties in a refrigerated truck on the way to the coast.
The dangerously-thin animal, first spotted in the Seine last week after veering off its normal path to the Arctic, was being prepared for transfer to a saltwater pool in Normandy.
It was to spend several days recuperating there before being towed out to sea.
The Conservation group Sea Shepherd France said veterinary exams after the beluga's removal from the river showed no indication of digestive activity. Veterinarians had planned to try to restimulate the whale's system.
The rescue team had said ahead of time that the transfer carried a risk of the whale dying because of the stress that the process involved.
The first stage of the failed rescue operation, which involved crane operators, 24 divers and a dozen veterinarians, had taken almost six hours.
The 4-meter (around 13-foot), 800-kilogram (roughly 1,800-pound) beluga whale had been stranded since Friday at a river lock in Saint-Pierre-La-Garenne, Normandy, some 130 kilometers (roughly 80 miles) away from the ocean. Activists were concerned from the outset for its health, as it had refused to eat.
Beluga whales are a protected species typically found in cold Arctic waters.
In May, a killer whale that had become stranded in the Seine was found dead after an operation to save it failed. The animal had been due to be euthanized because of its bad state of health.