The cellphone from which Howrah child kidnapper Rakesh Singh was negotiating a ransom for the release of his former colleague’s three-year-old son was found switched off on Sunday, shortly after cops had traced the call location to Gaya in Bihar.

Aman’s father Pappu Gupta, a Burrabazar trader, has joined a four-member team from Bally police station in Patna in a bid to re-establish contact with Rakesh.

Sources said police had advised the rest of the Gupta family in Bally and native state Bihar not to make any more “independent enquiries” about Aman — erroneously mentioned as a girl in The Telegraph on Sunday — because that might endanger his life.

Rakesh, 36, is suspected to have nurtured a grudge against Pappu for a long time, though he never showed it. The duo had worked together in a garments shop before Pappu set up a small business and his colleague and friend returned to his ancestral home in Nalanda, Bihar.

“We have yet to confirm what provoked the kidnapping but it seems there was a financial dispute between the two former colleagues,” said an investigator.

Rakesh’s brother-in-law Jayananda Singh, in whose house he was staying since arriving in Bally a fortnight ago, is under detention for allegedly playing a role in the kidnap-for-ransom plot.