Experts are baffled by the mass stranding of dolphins that took place on Monday morning, after post-mortems on a number of the animals revealed no poison or ill-health.

According to news reports, as many as 70 common dolphins were gathered in Porth Creek up the Percuil river near Falmouth, 33 of which became stranded. In the end just seven were rescued, 24 died and two had to be put down.

The British Divers Marine Life Rescue charity, which specialises in rescuing sea mammals stranded on British shores has suggested several possible causes.

The pod may have followed a school of mackerel up the river, however the charity’s chairman told the Daily Telegraph: “The fact that they have beached in four separate sites is very unusual.”

Powerful military sonar apparatus has been implicated in whale strandings before but the MOD has denied causing the strandings.

But another spokesman for the British Divers Marine Life Rescue charity has speculated that Killer Whales do sometimes venture into the English Channel and that this may have frightened the pod up the river and into trouble.

Scientists are continuing their search for clues as the rescuers stand down.

Click here for a full round-up of the latest news on the strandings