Last week, the Girish Park police received a letter from Sumita accusing the singer's nephew, with whom he had a joint account and a locker in a bank in Kolkata, of siphoning off cash and valuables, police sources said on Monday.
According to the letter sent by post from Bengaluru, where Mr Dey resided with his daughter and her husband, the joint account with the nephew was for the renovation of the singer's ancestral house in Kolkata, which he did not visit frequently because of his ailing health.
The money was taken out without the knowledge of Mr Dey or his family members, it said.
"We have started an investigation. Although a joint account holder can operate the account, we are verifying all aspects. We have not arrested anybody so far," DC (central) D P Singh said.