A pod of 77 pilot whales that died after washing ashore in Orkney were healthy before they became stranded, according to initial findings.

The animals were found on the island of Sanday on Thursday following what could be the largest mass stranding in nearly 100 years.

Cetacean specialists - whose expertise is in aquatic mammals - have been examining tissue samples to establish the cause of the stranding.

Mariel ten Doeschate, from the Scottish Marine Animal Stranding Scheme, told BBC Scotland News that thorough post-mortems had so far been carried out on about 30 whales.