The FIR in the death of the 45-year-old businessman was registered at the City Kotwali in Sultanpur district.
Shukla's family alleged that he died due to police torture. Along with residents in the area on Tuesday, the family had staged a protest demanding registration of an FIR against police personnel.
Shukla, aka Sajan Shukla, was allegedly involved in the loot of Rs 26 lakh from bank employees when the money was being transferred to a UCO Bank branch in a cash van on October 5, the police said.
The police claimed they had sufficient evidence to question him further, but family members alleged Shukla was interrogated twice earlier in the same case and was released due to lack of evidence against him.
Shukla's brother, Om Prakash, claimed the police personnel of Peeparpur police station in Amethi barged into their house around 3 a.m. on Tuesday.
They took his brother Sajan Shukla along wutrh his two sons Rahul and Sahil forcibly without giving any reasons to the family, he said adding that he and his family were later informed that he was tortured by police personnel following, which he died.
Shukla's two sons also claimed that their father was tortured and forced to admit to his involvement in the loot.
Superintendent of Police (SP), Amethi, Khyati Garg, refuted the allegations and said that it was not a case of police torture but Shukla had apparently consumed poisonous substances following which his health deteriorated.
The SP said the police team first got him admitted to a nearby community health centre and later shifted to Sultanpur district hospital where he died.
"We had sufficient ground for Shukla's detention and interrogation as he was suspected of tipping off his other accomplices about the cash movement. Moreover, he had a criminal background. He was also associated with dreaded criminal Zakir Ali alias Guddu," Garg said.
SP Sultanpur Himanshu Kumar said the FIR was registered on the complaint of Shukla's brother as the family were not allowing to carry out the post-mortem examination and other legal proceedings.
"Initially, no external injury was spotted on the deceased's body while the details of internal injury, if any, will be revealed only after the post-mortem examination," he added.
( With inputs from IANS )