Law firm Sidley Austin and accounting giant Deloitte were among professional services firms that reached a proposed $234 million settlement July 10 in a class-action case alleging links to Aequitas Securities LLC’s “Ponzi-like” scheme.

Three other defendants were part of the settlement that a plaintiff’s firm said is the largest ever for a securities lawsuit in Oregon. The agreement still must receive court approval.

Audit firm EisnerAmper LLP, TD Ameritrade Inc. and consultancy Duff & Phelps were also among the defendants in the settlement. Another law firm, Tonkon Torp LLP, reached a separate settlement earlier this year for $12.9 million.

The case was brought by investors in Aequitas Securities, which unraveled in early 2016 when the Securities and Exchange Commission said the once high-flying investment management firm was operating “in a Ponzi-like fashion.” Rather than investing clients’ funds in new assets, new clients were found to pay out older ones, the SEC’s complaint said.

The firm used a complex series of transactions and entities to make itself appear viable, but by the end of 2015 it owed $312 million in investor funds with “virtually no money to repay them,” the SEC said.

The lawsuit against the professional services firms said Sidley provided legal advice for Aequitas’ securities offerings since as early as 2014. Deloitte prepared audited statements for Aequitas in 2013 and 2014, the original complaint says.

A spokesperson for Sidley, which was represented in the case by Munger Tolles & Olson and Portland-based Markowitz Herbold, said the lawsuit ends “costly” and “burdensome” litigation.

“The plaintiffs did not allege that Sidley or the other six defendants knew about or were involved in the alleged fraudulent scheme perpetrated by Aequitas,” the firm’s statement said. “Two senior Aequitas executives pleaded guilty to conspiring to violate federal law in operating the funds and admitted to intentionally misleading investors and withholding information about the financial condition and business activities of Aequitas from their outside accounting and law firms.”

A TD Ameritrade spokesperson said class-action lawsuits are “costly” and “inherently risky” to defend against.

“While there has been no admission or finding of liability against TD Ameritrade, after more than three years we welcome the opportunity to help put an end to this litigation,” TD Ameritrade said in a statement, noting the company’s payout after insurance “is not material” to financial results.

“Given the high cost of litigation and the minimal involvement of our firm, we are pleased that this matter has settled,” an EisnerAmper spokesperson said.

Deloitte and Duff & Phelps did not immediately respond to requests for comment.

If the settlement is approved and a related liquidation of Aequitas’ assets is completed, class members could receive up to $311.6 million in gross recoveries, according to plaintiffs’ lawyers at Hagens Berman and Stoll Berne.