More than 25 people on Wednesday (11 February) flocked to the police headquarters in Hong Kong to complain over a scam involving the digital currency that media estimate could have duped investors of up to $387m (£253m).

On Tuesday (February 10), Hong Kong's central bank warned people "to exercise extra caution when considering making transactions or investments with Bitcoin".

One man, Bikash Gurung, said he had invested around HK$600,000 (£50,625, $77,400) six months ago with Mycoin.hk and while he had received a payment of HK$100,000 he knew in December something was wrong.

"Because we can see that Mycoin.hk, they separate totally the price of real bitcoin. So after that we know that they are cheating us, something like that," said Gurung, a Nepalese businessman who has lived in Hong Kong for nine years and heard through MyCoin.hk through friends.

A police official declined to say how many complaints had been made, but said a statement would be issued.

The company at the centre of the scam, MyCoin, describes itself on its website as a "leading global Bitcoin trading platform and application service provider".

MyCoin promised clients a return of HK$1m over a 4-month period, based on a HK$400,000 investment that would produce 90 bitcoins on maturity, the South China Morning Post reported on Monday.

It claimed to have 3,000 customers investing an average of HK$1 million each, the paper said.

President of the Bitcoin Association of Hong Kong, Leonhard Weese, said the company's website raised many red flags and that it seemed be similar to a Ponzi scheme.

"I don't think they ever had a bitcoin mine, they never had the bitcoin mine that they advertised, the website for their bitcoin mine shows only very generic information about bitcoin. It doesn't show any information about what people would be interested in when they invest in a bitcoin mine - where is it?

"What are the specifications? How large is it? Who is maintaining it? All these things, all these information are missing. So I very much doubt they ever had a bitcoin mine. They used the investments from new customers to pay out the returns from older customers," said Weese.

The price of a bitcoin has slumped from a late-2013 high of above $1,000 to around $220, according to CoinDesk's price index.

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