Mystery of dolphin mass stranding

Initial post-mortem examinations of some of the 26 dolphins found dead in Cornwall have so far revealed no clues as to the cause of the mass stranding.

The animals appear to have been well-fed and there were no obvious signs of disease or poisoning.

The dolphins died when they became trapped in a river creek off the Fal estuary on Monday.

Confusing sonar signals from ships are among the possible causes being considered by wildlife experts.