Accounting firm Mazars Group has suspended all work with its crypto clients. The decision to cut ties with Binance, KuCoin and Crypto.com comes just after the global accounting firm released “proof of reserve” reports for several digital asset exchanges.

The move comes as major cryptocurrency exchanges look to prove their solvency, and show they have enough money to cover customer withdrawals. The CEOs of Binance and Crypto.com have looked to distinguish their own business practices from what happened at FTX, which has been charged with illegally using customer deposits for years before filing for bankruptcy. Its founder, Sam Bankman-Fried, is facing multiple counts of fraud and money laundering.

Mazars fired the Trump Organization as a client in February, citing a lack of reliability in the organization’s financial statements.

Mazars Group said in a statement to CNBC that it had “paused its activity relating to the provision of Proof of Reserves Reports for entities in the cryptocurrency sector due to concerns regarding the way these reports are understood by the public.”

The statement added Mazars’ proof of reserves reports are “performed in accordance with Reporting Standards relevant to an Agreed Upon Procedures report.”

“They do not constitute either an assurance or an audit opinion on subject matter. Instead they report limited findings based on the agreed procedures performed on the subject matter at a historical point in time,” the statement continued.

A spokesperson from Binance, the world’s largest crypto exchange, told CNBC in a statement that, “Mazars has indicated that they will temporarily pause their work with all of their crypto clients globally, which include Crypto.com, KuCoin, and Binance.”

“Unfortunately, this means that we will not be able to work with Mazars for the moment,” Binance said.

Both bitcoin and Binance’s BNB token took a dip on the news, with bitcoin initially dropping nearly 3% and Binance’s native token falling close to 5.5%.

Mazars’ South African branch published a five-page proof of reserves for Binance on Dec. 7, but the report is no longer available on the firm’s website as of Friday morning. Unlike standard audits, the proof of reserves for Binance only accounted for bitcoin. The report did not show liabilities for Binance’s lending arm. Binance CEO Changpeng Zhao has often said that the company itself has no debt.

On Dec. 9, Crypto.com published a proof of reserves audited by Mazars, attesting that customer assets were held on a 1-to-1 basis, meaning that all deposits were 100% backed by Crypto.com‘s reserves. A spokesperson for the exchange reiterated that the firm had “successfully” completed its recent proof of reserves in collaboration with Mazars and that the accounting company had “provided independent verification of our secure on-chain digital assets matching our customer balances 1:1.”

Crypto.com added that customers can verify their balance on its website. A spokesperson said the company will “continue to engage with reputable audit firms in 2023 and beyond” as they “seek to increase transparency across the entire industry.”

KuCoin said its proof of reserve report was already delivered by Mazars. ”In the future, we are open to work with any leading and reputable audit to provide the third-party verification report,” a KuCoin spokesperson said.

Meanwhile, Ernst & Young, PricewaterhouseCoopers, Deloitte and KPMG — collectively dubbed accounting’s Big Four — haven’t made moves to drop their crypto clients. Coinbase, for example, is a client of Deloitte. Tether uses Moore Cayman.

The Big Four did not immediately respond to CNBC’s request for comment.

In an interview Thursday on CNBC’s “Squawk Box,” Zhao said Binance is working with auditing firms, though he didn’t name which ones. He added that “interestingly, many audit firms are kind of scared to work with crypto businesses.”

“There are a few audit firms that audited FTX and they got burned because they give the stamp of approval, and I don’t know how they did the audits. But audits don’t reveal every problem,” continued Zhao, noting that many of those firms “don’t know how” to audit crypto changes.

“They don’t know how to audit user assets, different blockchains,” he said.