A stuntman who entered the Ganges river on Sunday tied up with steel chains and rope is missing, police said.
Chanchal Lahiri, known by his stage name "Jadugar Mandrake", was lowered into the river by crane as family members, media and police watched from the banks.
But the 40-year-old failed to emerge from the water, triggering a frantic search by authorities.
"We are still searching," a family member told news agency AFP.
Mr Lahiri earlier said he had successfully pulled off a similar stunt 21 years ago at the same venue.
"I was inside a bullet proof glass box tied with chain and locks and dropped down from Howrah bridge. Then I came out within 29 seconds," he told AFP.
He admitted it would be tough to free himself this time.
"If I can open it up then it will be magic, but if I can't it will be tragic," he said.
When Mr Lahiri tried the stunt at the river in 2013, he was assaulted by onlookers who saw through his escape from a locked cage via a door that was clearly visible.