The money belonging to the Motor Vehicles, Purulia, was deposited at the cash counter at around 10.30 am, the Branch Manager, Santanu Das said.
Before the cashier could remove the cash from the counter, a person arrived and asked the cashier to assist him in retrieving a Rs 10 note that had fallen near the cashier's chair behind the counter, the Manager said.
As the cashier bent down to pick up the note, the unknown person disappeared with Rs 3.50 lakh from the counter, the Manager said.
A police official said the bank's CCTV footage showed a man leaving the counter with the cash. No arrest has yet been made.