Seema Devi's remains were found at the site two-days after the ceremony and sent for post mortem, which was conducted by a panel of three doctors, Superintendent of Police (SP) Ratankant Pandey said.
The post mortem report confirmed that Devi died due to suffocation, he said.
The SP said she was apparently deranged and had hid herself inside the bonfire.
The incident came to light on Saturday when people found the woman's body while collecting ashes from there.
No foul play is suspected, he said.