Marine life experts monitoring more than 60 pilot whales have found they have returned to the spot where they risked becoming stranded on the shores of Loch Carnan, off South Uist in the Western Isles.

They arrived last Thursday – many with head wounds – suggesting they had injured themselves in the shallow waters. Later they were spotted in deeper water and were thought to be out of danger, only to return hours later. One appeared to have died. Dave Jarvis of the charity British Divers Marine Life Rescue said the animals did not seem to be agitated. "Unfortunately the pod of pilot whales moving away from the Scottish sea loch earlier have now returned to their original location.

"The animals retraced their route back into the loch. Sadly, it is thought that one of the animals may now have died as a body has apparently been seen in the water."

Jarvis said the whales could only get stranded at one place – a sandy section of beach at the loch. However, other dangers are posed by the rocky coastline, with its many inlets and bays.

Volunteers from the charity will continue to monitor them.

The Scottish government has also lent rescuers a fisheries protection boat to follow the animals' movements. A rigid inflatable boat was deployed from the vessel to investigate the apparent death of the whale.

Inflatable pontoons are available to help float any beached or stranded whales if needed.

Last year, in October, some pilot whales almost got stranded in the same sea loch. Less than a week later, 33 whales, believed to be the same group, were found dead on a beach in Donegal.

Pilot whales prefer deep water, but come inshore to feed on squid, their main food.

Last week, a pilot whale died after getting stuck in the Sullom Voe inlet in Shetland. An autopsy was carried out but the results are not yet known.