The IIT professor-turned-monk who died fasting for a cleaner Ganga on Thursday had written six letters to Prime Minister Narendra Modi without success, his spiritual guru has said while demanding a CBI probe into his death.

Swami Avimukteshwaranand, a sadhu based in Modi’s constituency of Varanasi, suggested that Swami Gyan Swaroop Sanand had died under “mysterious circumstances” at AIIMS Rishikesh after being forcibly taken there from his protest spot in Haridwar on Wednesday evening.

“The way the police picked him up from Matri Sadan (his ashram) and he died (at the hospital) raises doubts over the state government’s intentions,” he said.

Dr Ravi Kant, director of AIIMS Rishikesh, said the monk died of a heart attack. “He was suffering from long-term hypertension, hernia and urinary diseases. His potassium and glucose had reached critical levels. We talked to him on Thursday morning but he died at 1.50pm.”

Sanand, 86, died after a 111-day fast demanding a stop to illegal sand mining on the Ganga’s riverbed and banks and a halt to all dam and hydel projects on the river.

“His fellow sadhus at Matri Sadan have revealed that river development and Ganga rejuvenation minister Nitin Gadkari had spoken to him on the phone a few days ago and said his demands wouldn’t be met even if he died fasting,” Avimukteshwaranand alleged.

State BJP leaders declined comment on the allegation.

Avimukteshwaranand said Sanand had written six letters to Modi since February but his demands were ignored.

“He wrote on February 24, June 13 and June 22 --- the day he began his hunger strike. He said the mining and river projects posed a threat to the Ganga and its neighbourhood but the Prime Minister, who claims the Ganga is his mother, ignored him,” Avimukteshwaranand said.

“He again wrote to the Prime Minister on June 23. The next letter was sent on August 5 through Uma Bharati, drinking water and sanitation minister, when she met Sanand at his ashram. The last letter was written on September 9, mentioning all his previous letters, while informing Modi that he would stop drinking water from October 10.”

Avimukteshwaranand, who had given diksha to Sanand on July 3, 2011, suggested the state government hand the body over to Banaras Hindu University, where Sanand had spent his formative years.

But the AIIMS Rishikesh director said: “The saint-environmentalist had donated his body to AIIMS Rishikesh. We will keep it for medical purposes.”

Sanand was born G.D. Agrawal in Muzaffarnagar, western Uttar Pradesh, and did his BSc from Banaras Hindu University before earning a BTech in civil engineering from IIT Roorkee. He obtained a doctorate in environmental engineering from California University and returned to teach at IIT Kanpur.

Vishwambhar Nath Mishra, chief priest of Varanasi’s Sankat Mochan temple and a professor at IIT-BHU, said: “Sanand had not placed any big demand before the government. The government only pays lip service to the Ganga. We would have had Sanand with us today had the government shown some honesty.”

Uttarakhand chief minister Trivendra Singh Rawat issued a media release saying his government and the Centre had been in constant touch with Sanand and would have needed time to study his demands.

He mentioned Uma Bharati and MP Ramesh Pokhriyal meeting Sanand and Gadkari speaking to him over the phone.

“The state government has shown great sensitivity on this issue.... We tried our best to save his life but despite all efforts, he refused to break his fast. The doctors at AIIMS also tried their best to save his life,” he said.