“The incident took place at Bamuni area of Barhampur on Wednesday. Our officials got to know about it on Thursday. Teams of forest and veterinary officials are at the spot to take stock of the tragedy,” Nagaon, deputy commissioner Kavitha Padmanabham said.

The deaths took place in an area with small hillocks and forests. Officials suspect the elephants, which were part of a herd, were staying close to each other when lightning struck. While four bodies were found at the bottom of a hillock, 14 others were found at the top.

“Preliminary investigation of the spot suggests lightning could be the reason for the deaths. All the elephants killed were adults and sub-adults,” Vasanthan, divisional forest officer (Nagaon), said.

“We are trying to recover all the bodies and conduct post-mortem. The exact cause of the deaths would be known only after the results are out, most likely by Friday,” he added.

Wildlife experts confirmed that the incident was the single largest instance of deaths of wild elephants in one go. They also suspected that there could be other reasons as well for the deaths.

Chief Minister Himanta Biswa Sarma has expressed shock and anguish at the deaths of the elephants and directed forest and environment minister Parimal Suklabaidya to visit the spot immediately.

“A tragedy of such scale is unheard of in Assam. It is a big loss. While lightning has been suspected to be the cause, mass poisoning of the pachyderms shouldn’t be ruled out,” said Bibhab Talukdar, noted elephant expert and CEO of Aaranyak, a Guwahati-based wildlife NGO.

“Assam has witnessed poisonings of wild elephants in the past, though not on such a large scale. I hope a thorough probe is done to know the exact cause behind the deaths,” he added.