A major rescue operation was under way today after a pod of 15 dolphins became stranded in a river, causing many more to follow them.
Coastguards said the first pod of dolphins swam up the Percuil River near Falmouth, Cornwall, before they were beached in Porth Creek.
It is understood most of the pod died and coastguards believe their distress signals have lured other dolphins to the river.
Teams of conservationists, divers, coastguards and local government officials are now in the area attempting to send the dolphins back out to sea.
A spokesman for Falmouth Coastguard said: "We first heard a pod of dolphins had got stranded in Porth Creek at around 8.30am.
"Around 15 of them are beached on the banks of the river and most of the pod have died.
"There are now many more following the same route in. We are not sure why they are all swimming up the river - it seems they are following the distress calls of the first pod."
Tony Woodley, national spokesman for British Divers Marine Life Rescue, said the charity would put all its resources into the operation.
Mr Woodley said this was the biggest mass stranding of marine life for 27 years and warned most of the dolphins would probably die.
He said: "We haven't seen a stranding anywhere near this scale since 1981 when pilot whales were beached on the east coast.
"This is extremely rare.
"We are warning people that many will die but we may be able to save some."
Mr Woodley said the species were striped dolphins which were not naturally a coastal breed.
He said they were ocean going and had probably followed in fish who were feeding on a large algal bloom in the area.
Mr Woodley said: "Logistically a rescue like this is a minefield, it is very difficult to manage.
"You have to get all the dolphins together, if one or two leave the river system they will just come back to rejoin the main social group.
"We have one of the best teams of volunteers in Cornwall and they will do everything they can. We have also asked for help from divers in Devon."
A spokeswoman for the RNLI said three volunteer lifeboat crew members managed to help five dolphins back out to deeper water.
The Falmouth RNLI Atlantic 75 inshore lifeboat was called to the scene this morning and the volunteer crew were shocked to find what they described as "carnage".
They said many of the dolphins were already dead, with others struggling in the shallow waters or on the river edge.
Helmsman Dave Nicoll said two of his crew got in to the water with the dolphins.
He said: "It's a horrible scene of carnage with bodies everywhere, but we are doing our best to help and will continue to support the expert groups.
"We have been trying to help those who are alive and have already succeeded in getting five back into the water.
"We think the pod have been attracted by the cries for help from those that are stuck in the creek."Reuse content