The van was standing outside the ATM of a Bank of India branch when the incident took place, said Superintendent of Police Siddharth Bahuguna.
As cash was being loaded in the ATM, a man walked upto the van driver, saying he had dropped a Rs 500 note.
The driver stepped out to pick up the note when a second person grabbed a box containing Rs 43 lakh in cash from the van and ran away, Bahuguna said.
The driver and his colleagues who were loading the cash in the ATM immediately alerted the police, he said.
It was not known whether the two men used a motorcycle or any other vehicle to escape after running away with the box, he said.