Coinbase inc., the leading cryptocurrency exchange, admitted Thursday that a glitch had accidentally charged some of its customers multiple times for a single purchase — with some users saying their bank accounts were drained by the error.

Outraged customers have been complaining on Reddit for days about the unauthorized charges. One user reported they were charged 17 times for a $1,000 purchase. Another said a $300 purchase of bitcoin BTCUSD, -1.58% , ether and Litecoin was duplicated five times, to disastrous effect.

“My bank account went from very comfortable to negatives balance, not to mention extra $5 charges, and overdraft fees. As a result my rent check bounced, and my bank went further into negative for a NSF charge for $25. My landlord is not a nice person and is on my CASE and I have nothing to offer him. I am FREAKING OUT,” that person said on Reddit.

Other Reddit users also reported their bank accounts were drained.

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In a series of statements Thursday on Reddit, San Francisco-based Coinbase said: “We have confirmed that this is an issue occurring downstream from Coinbase, and we’re working with those parties to reach a resolution.”

“We know this experience is frustrating. We are actively working with the card networks and processors to investigate these issues,” Coinbase said in a blog post. “Coinbase will ensure that each affected customer will be refunded in full for any erroneous charge. Our processor confirmed that any erroneous charges will be refunded over the next few days.”

The exchange blamed recent changes to how credit-card issuers were handling charges and fees for cryptocurreny purchases. Earlier this month, Coinbase told customers that because of the changes, payments for digital-currency transactions were now being processed as cash advances, which could result in additional fees.

On Friday, Coinbase and Visa Inc. V, -1.29% issued a joint statement saying: “This issue was not caused by Coinbase.”

Visa, though, did not say it was to blame. While Coinbase said in a tweet late Thursday that the errors were “the result of Visa reversing and recharging transactions,” Visa, in a statement reported by The Verge, denied it had made changes to transaction codes.

Coinbase said transactions between Jan. 22 and Feb. 11 may have been “refunded and reprocessed — resulting in erroneous charges.” Friday’s joint statement said “all reversal transactions have now been issued, and should appear on customers’ credit card and debit card accounts within the next few days.”

This report has been updated to include Visa’s statements.