A dead Fin whale measuring 56ft (17m) long has washed up in north Cornwall.
The putrefying carcass was first spotted five days ago off Pendeen and washed up on shore 37km (23miles) away at Porthtowan beach on Sunday evening.
It is not known when the female whale died or the cause of its death but Cornwall Wildlife Trust believe it was most likely to have been hit by a ship.
People are being urged to keep clear of the whale, which may be diseased, as they risk being cut off by the tide.
Jan Loveridge, co-ordinator of Cornwall Wildlife Trust Marine Strandings Network, said that although dead dolphins and harbour porpoises often got stranded on Cornish beaches, it was rare for a whale to become stranded.
"The whale at Porthtowan is very decomposed and although there is no obvious cause of death, this species is particularly vulnerable to ship strikes and if they do get hit, they seldom survive," she said.
"We believe this is the most likely cause of what happened to this whale.
"This is a very good opportunity to take some samples for research purposes which will be sent off to our partners at the Institute of Zoology in London.
"We are urging people not to go down to the beach as the whale could be a health hazard and there is a risk of cliffs crumbling in the area and people getting cut off by the tide."
Cornwall Council is currently assessing the situation with regards to removing the carcass from the beach.
Fin whales are the second largest animals in the world and are seen most winters off the coast of Cornwall.