A pair of Democratic senators called on the Public Company Accounting Oversight Board (PCAOB) to address so-called “sham audits” of cryptocurrency companies by registered auditors in the aftermath of the collapse of FTX.

Sens. Elizabeth Warren (Mass.) and Ron Wyden (Ore.) raised concerns with the PCAOB about the “independence and methodology” of audit firms doing work for cryptocurrency companies, urging the regulator to “ensure auditor accountability and the credibility of the auditing system.”

“When PCAOB-registered auditors perform sham audits—even for firms that may lay outside of the PCAOB’s jurisdiction—they tarnish the credibility of the PCAOB and undermine confidence in the PCAOB-registered auditors that investors and the public rely on when making investment decisions,” wrote the senators Wednesday in a letter addressed to PCAOB Chair Erica Williams.

Audit-related work at cryptocurrency companies that are not publicly traded falls outside of the PCAOB’s jurisdiction. But the senators pushed Williams to hold those firms accountable for the work they perform for crypto companies.

“[I]f the auditors who scrutinize large public companies are the same ones who whitewash ‘audit’ results for crypto firms with demonstrated histories of malfeasance, investors and the public will not have confidence in any of these audits,” the senators wrote in a press release.

The senators focused their ire on firms that had done work for FTX, a list that reportedly includes advisory services by Deloitte and PwC of the Big Four. The cryptocurrency exchange touted it passed generally accepted accounting principles (GAAP) audits performed by Armanino and Prager Metis in the days leading to its November bankruptcy.

Armanino and Prager Metis “failed to identify the alleged ‘old-fashioned embezzlement,’ ‘unprecedented’ lack of recordkeeping,’ and ‘utter failure of corporate controls’ at the heart of FTX’s collapse,” the senators wrote, citing comments made about the exchange by its new Chief Executive John Ray, who is overseeing its bankruptcy.

Beyond FTX, the senators singled out so-called “proof of reserve” reports developed for cryptocurrency companies by audit firms as problematic. The reports purport to verify the financial health of cryptocurrency companies by asserting they have enough funds to cover customer deposits, but their findings “fall significantly short of real audits” despite crypto companies promoting them as such, the senators wrote.

The senators demanded Williams answer a series of questions by Feb. 8 about what the PCAOB, which is overseen by the Securities and Exchange Commission (SEC), is doing to mitigate the potential harm being done to the auditing profession by these activities.

They asked whether the regulator has the authority to strip auditors of their PCAOB-registered status “if they provide services or engage in conduct that fall short of PCAOB standards and rules, even if those actions are taken in relation to private, non-SEC registered companies?” Another question suggested since banks, publicly traded companies, and registered investment firms have crypto assets on their books, the PCAOB should describe “the standards by which auditors must abide when evaluating the risk of exposure to crypto firms or validating the valuation of crypto investments.”

In a separate speech delivered at an American Economic Liberties Project virtual event Wednesday, Warren said cryptocurrency firms should be regulated by the SEC, either with the tools the agency already has or with new authority granted by Congress.

“The SEC has a long history of fighting exactly the battles that we now face,” she said. “From the time of the commission’s creation, its job has been to protect consumers by making sure that investors have access to the whole truth about investment risks, that they’re treated fairly in the market, and that wrongdoers face meaningful consequences.”

Other agencies, like the Commodity Futures Trading Commission (CFTC), have asserted they are the right choice to regulate cryptocurrencies. CFTC Commissioner Christy Goldsmith Romero argued in December the agency should tighten regulation of cryptocurrency with the tools it already has, while CFTC Chairman Rostin Behnam last July pressed Congress to grant the agency more authority to oversee the industry.