(CNN)Sri Lankan rescuers have returned 100 whales to sea after a mass beaching on Monday, the country's navy has said.
Scores of short-finned pilot whales began coming ashore at Panadura, 25 kilometers (15 miles) south of Colombo, on Monday afternoon, and authorities were mobilized to help them back to sea.
Locals joined officials from Sri Lanka's navy and coast guard in tending to the whales.
Sri Lanka's Marine Environment Protection Authority (MEPA) told AFP news agency that it was the largest single pod of whales stranded in the South Asian country.
A dead pilot whale on a beach on Sri Lanka's western coast after the mass stranding.
"It is very unusual for such a large number to reach our shores," MEPA chief Dharshani Lahandapura told AFP, adding that the cause of the stranding was not known.
Rescue teams worked through the night with assistance from the navy, coast guard, lifeguards, and residents.
"On the request of Commander of the Navy, Vice Admiral Nishantha Ulugetenne, Jet skis provided by a local water sports club were utilized to pull the whales back into the ocean throughout the day and night," the Sri Lanka Navy statement said.
The death of four whales is being investigated. The navy said that the whales might have followed one whale off course and become stranded.
In September, nearly 500 whales beached in Tasmania, Australia, in that state's largest ever beaching. At least a third died during rescue attempts.
Whales are highly social animals and travel in pods, but the causes of mass strandings are not clear.