Visa and Worldpay have been thrust into a swirling controversy over erroneous charges that hit traders using Coinbase, America’s biggest cryptocurrencies exchange.

Over the past two days, a flood of Coinbase users have complained about unexpected charges hitting their bank accounts. “You drained my bank account and now I have nothing,” claimed one user on Reddit. Another called the transactions “a breach of my personal security”.

The issues shine a light on the intersection between the traditional financial industry and the burgeoning digital currencies sector.

Coinbase has denied that it is to blame for the duplicate charges. “We’ve been informed by relevant payments network authorities that this was not caused by Coinbase,” said Daniel Romero, general manager at Coinbase in an interview late on Friday with the Financial Times.

The problems have only affected users who have paid with Visa cards, according to a person with direct knowledge of the situation.

But Visa has also deflected blame, saying in a statement that it “has not made any systems changes that would result in the duplicate transactions cardholders are reporting.” It said, however, that it stands ready to work with intermediaries to “ensure cardholders are protected from unauthorised transactions”.

Worldpay, which processes credit and debit card transactions for Coinbase, said late on Friday that it too is looking into the issues. A spokesperson said: “We are actively working with and engaging all parties involved — including the card networks, issuing banks, other processors and Coinbase — to resolve this issue.”

The problems faced by Coinbase customers, and the lack of clarity on who is to blame, highlights the perils faced by participants in the nascent industry.

Coinbase and other exchanges have grown rapidly thanks to a rush of customers over the past few months as cryptocurrency prices fluctuated and captured the attention of a wide range of media outlets.

It has previously faced other user complaints, including from some who have said that withdrawals in various currencies, including US dollars, have been delayed.

In January it hired an ex-Twitter vice-president to bolster its customer services department, which it has said was overwhelmed by the booming demand.

Cryptocurrencies exchanges across the world have faced sometimes serious issues as they tap into the burgeoning digital currencies business. Japan’s Coincheck suffered a $500m hack earlier this year. Binance earlier this month was forced to suspend trade and withdrawals for more than 24 hours as it faced problems with a system upgrade.

Regulations have generally not kept up with the market’s rapid growth. In the US, exchanges are generally overseen by state securities regulators, leading to a fragmented system.

Chris Giancarlo, chairman of the Commodity Futures Trading Commission, on Thursday told a Senate hearing that “a rationalised federal framework may be more effective and efficient in ensuring the integrity of the underlying market” in virtual currencies.”

The finance ministers of Germany and France also this week called for a clampdown on digital currencies, writing in a letter to other G20 finance heads that digital tokens “could pose substantial risks for investors” and potentially to longer-term financial stability.

This article has been updated.

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