The DG said he had received the mail, sent from a Yahoo account, on December five.
"That mail was received not only by me but also countrywide by police officials," he said.
Another senior police officer said, however, said it appeared to be a fake e-mail, "yet information has been sought from Yahoo's Singapore office in this regard".
All the district police chiefs had been asked to remain alert soon after the message was received, Rath said.