Guwahati, Even as the authorities are saying that the 18 wild elephants were killed after being struck by a massive 'lightning' bolt in central Assam's Nagaon district, the wildlife experts are saying the tragic incident is very "mysterious" and demanded a thorough probe.

Nagaon district Deputy Commissioner Kavitha Padmanabhan said that a team comprising wildlife, forest and veterinary department officials went to the forest areas to ascertain the exact cause of the deaths of 18 elephants including calves on Wednesday night in the mountainous Kandali Proposed Reserve Forest (PRF).

"Before getting the reports of the official team, I am unable to give all the details of the 18 dead elephants," Padmanabhan told IANS over phone.

Various organisations and wildlife experts have demanded in- depth inquiry by independent agencies to know the exact reasons for the death of so many wild elephants at one time.

Wildlife expert and former top official of the Assam government Annarwaruddin Choudhary demanding a thorough probe termed the incident as very mysterious.

"If the elephants died due to the thunderbolt, there might be some burn injuries and other effects of the lightning at the spot. But whatever visuals I have seen there are some doubts about the nature of the death of the elephants," Choudhary told IANS over phone.

He said that the bodies of the animals were scattered in the jungle and circumstantial signs of 'lightning' were not visible clearly.

"Only the post-mortems of the bodies of the dead elephants would reveal the cause of the deaths," he added.

Green Guard Nature Organisation (GGNO) Secretary General Rituraj Phukan said that there is no telltale evidence visible in the images and videos circulating on social media.

"The GGNO, which has been working in the area since two decades, requested the government to conduct a thorough and independent inquiry to assuage the concerns of conservationists and wildlife lovers all over the world," said Phukan.

Following the directions of Assam Chief Minister Himanta Biswa Sarma, Environment and Forest Minister Parimal Suklabaidya accompanied by senior forest, wildlife and veterinary department officials visited the forest areas on Friday.

After visiting the area Suklabaidya tweeted: "The preliminary report of enquiry has been asked to be submitted within three days and a detailed investigation report within 15 days. We will unravel the exact reason behind their tragic deaths soon."

Assam's Forest (Wildlife) Department has constituted an 8-member team headed by Deputy Conservator of Forest (Publicity) K.K. Deori to probe the death of the 18 elephants.

Additional Principal Chief Conservator of Forests (WL) and Chief Wildlife Warden M.K. Yadava issued a notification constituting the inquiry committee which would submit a preliminary report within three days and the final report within fifteen days.

The notification said that the investigating officer would undertake detailed investigation of the site including water and salt lick quality, and may engage experts and agencies for the purpose, and carry out detailed fact-finding from fringe communities and first informants.

Yadava, quoting local wildlife officials, said that 18 elephants have died and lightning is the most likely cause of the deaths.

Local people informed the forest officials that the carcasses of the elephants were scattered at different places in the deep forest area.

Yadava said that cases are often reported of lightning striking animals and five elephants had died due to this in West Bengal recently, but Wednesday's incident in Nagaon is huge and terrible.

The district has had cases of man-animal conflicts.

The world famous Kaziranga National Park and Tiger Reserve (KNP & TR), one of India's seven UNESCO world heritage sites in the natural and environment category since 1985, also falls in five districts of Assam, including Nagaon.