Two bike-borne assailants allegedly committed the crime as the guards reportedly got down from the cash van of SSMS (Scientific Security Management services) company.
"They snatched the bag and sped off within a few seconds," a senior police officer said.
Police said it suspects an insider's role in the incident as one of the guards claimed to have fired at the assailants.
"It is difficult to believe that the bullet did not hit them as the guard shot at them from a very close range," the officer said adding that all angles are being looked at.