TOKYO (Reuters) - An elderly man nearing death who wants to give something back to the world, or just a prankster?

The mystery of who is leaving envelopes of 10,000 yen ($82) bills in men’s toilets at government offices around Japan has gripped the nation this week despite the existence of far weightier issues, such as a looming election.

Since April 9, some 4 million yen ($32,720) has been found in men’s rooms from the northernmost island of Hokkaido to the southern island of Okinawa, Japanese media say. Virtually all has been found in government office buildings.

The bills are individually wrapped in traditional Japanese “washi” paper with the word “remuneration” handwritten on the outside in ink.

Each comes with a handwritten letter in formal wording evoking Buddhist language, saying the giver hopes the money will be “useful for your pursuit of knowledge.”

Newspapers have devoted lengthy articles to speculation about the identity of the unknown benefactor, and the mystery dominated evening news programs on Wednesday. One domestic news agency even sent out urgent alerts as the number of bills found mounted.

The only thing everyone agrees on, given where the money is found, is that the person leaving them is a man.

The wording of the letter suggests a man with strong religious beliefs to some experts quoted in the media, while others think he is a former civil servant trying to cheer those in the same job, often the target of citizen anger.

Still others believe the message may actually be a sarcastic reproof telling civil servants to clean up their act.

Handwriting experts say the letters are all written by the same person, whose shaky handwriting suggests somebody elderly or seriously ill, and note that the writing has worsened over the months since the first set of bills was found.

“The fact that the letters end with the phrase ‘please be happy’ points to somebody who’s unhappy themselves -- who’s perhaps facing up to their death and wants to give something back to the world,” the Asahi Shimbun quoted one expert as saying.

But others think the man is a prankster who wants to create a stir in society while remaining unknown. Their proof is that the envelopes are left in toilets -- which lack security cameras.

The money has been handed to the police, but if nobody claims the cash within six months it will be given to the finders.