At least 45 whales died after they washed ashore overnight on a beach in Tamil Nadu's Tuticorin district, officials said on Tuesday, with experts attributing the deaths to a possible underwater disturbance like an earthquake or volcano. Helped by local fishermen, workers of the Tamil Nadu fisheries department, police and the administration managed to save 36 whales of the pod -- or group -- by towing them back to sea on Tuesday, officials said. While beaching of whales and other aquatic animals is common around the world, experts said it was rare to find such a large number of whales washing up ashore and hinted at the mammals being disoriented by underground activity. Officials said that the pod of 81 short-finned pilot whales had beached near Mandapu village since Monday evening. The area is around 600 km south of Chennai. "It appears the whales are in shock. It mainly happened due to unusual activity deep inside the sea," said a scientist with the Chennai-based Central Marine Fisheries Institute. A team of experts have also rushed to the village for an on-the-spot assessment of the cause. Pilot whales - known to be among some of the most social aquatic mammals -- are so named because they are led or 'piloted' by a leader in their search for food or breeding grounds. A forest department official who had visited the beach said there were injury marks on the dead whales which indicated "high intensity" underwater activity. "This may have happened hundreds of kilometres away and the whales may have been washed to the coast because of the tide," said the official who did not give his name. Rescue workers and fishermen worked through the day to pull the whales -- each weighing between 1 tonne to 1.5 tonne and measuring between 8 feet and 10 feet -- back into the sea. Ten fishing boats and one mechanised fishing made several sorties, each ferrying one whale at a time to sea and returning for more on the shore. Local residents said that the last time they saw such a large number of whales beaching was way back in 1973 when 140 whales had washed ashore. Many of them had died.