A mysterious benefactor has begun a social media frenzy in San Francisco, tweeting clues that lead his followers to hidden envelopes filled with cash.

Operating under the Twitter handle @HiddenCash, the anonymous user has been leading scores of people on city-wide scavenger hunts since Friday, with winners pocketing $100 (£59) each time.

Perhaps unsurprisingly, the profile's following has boomed since it was created last week, up to more than 115,000 and counting.

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According to the profile description, Hidden Cash's creator sees the hunts as "an anonymous social experiment for good".

He or she has encouraged those who find envelopes to send a picture via email or tweet one @HiddenCash, and has offered to provide advance clues for future "drops" to those who do.

Previous posts have described the user as having made his money from the San Francisco property market, and that he hopes winners will also "pay it forward" in any way they can.

Other posts give clues to suggest that the profile may be more of a collective effort. One reads: "Overwhelmed with joy at the following and love coming our way. Planning to keep on giving for the foreseeable future."

Another said: "Because people asked, just want to say that @Hiddencash is NOT instead of charity. We support many charities too. This is for fun."

Adam Wenger, a 27-year-old web producer, told reporters he won $200 dollars finding two envelopes in the city's South of Market District. He bought pizza for his co-workers and will pay a $100 dollar parking ticket with his cash.

The response to Hidden Cash has been overwhelmingly positive, even among those who fail to be first to the bundles. User Steve Devine wrote: "Missed the 'ladies' drop by less than five minutes but met a few other really cool 'searchers' and you've given me a great weekend. Thank you!"

Late last night local time (7.03am GMT), Hidden Cash tweeted an advance warning that drops would be taking place in San Jose in the morning "showing the South Bay some love and cash". So if you happen to be in San Francisco, you may want to get down there early.