Big Four firm PwC is under investigation for its audit of Wyelands Bank as part of a larger U.K. review linked to the recent collapse of Greensill Capital.

Wyelands Bank is owned by steel tycoon Sanjeev Gupta’s GFG Alliance, a metals-to-finance empire which was closely linked to Greensill, the supply chain financing company that went bust in March. The Financial Reporting Council (FRC) on Monday also announced accountancy firm Saffery Champness, Greensill’s auditor, is being probed for possible audit failures in the run-up to the company’s collapse.

The FRC is investigating PwC in relation to its audit of the consolidated financial statements of Wyelands Bank—which has closed for business and is going to be either sold or wound up—for the year ended April 30, 2019, while Saffery Champness is being investigated over its audit of Greensill for the year ended Dec. 31, 2019.

Both firms say they are cooperating with the regulator.

“It’s understandable that there is regulatory scrutiny in situations like this,” a PwC spokesperson said. “We will cooperate fully with the FRC in its inquiries. We share the FRC’s commitment to audit quality and are two years into a wide-ranging program to enhance audit quality across the firm.”

At this stage, the FRC has not noted any specific concerns about either firm’s work.

However, a source close to the investigation said, “There’s obviously a high degree of scrutiny of the Gupta and Greensill businesses from regulators, so perhaps it is to be expected this has extended to audit, too.”

The downfall of both Wyelands and Greensill has brought into question the state of audit scrutiny in the United Kingdom, as well as exposed concerns about gaps in regulatory oversight, effective monitoring, and the time it takes for an investigation to lead to enforcement action.

Gupta took over Wyelands (formerly Tungsten Bank) in 2016 under EU rules allowing a change in control to proceed unless a regulator had specific grounds for objecting. Now that the United Kingdom is no longer part of the European Union, the Bank of England (BoE) has suggested tightening the rules by forcing prospective owners to demonstrate they are fit to run a bank to avoid the same scenario from happening again.

In May, BoE Governor Andrew Bailey said the Prudential Regulation Authority, the bank’s regulatory arm, had launched an investigation into Wyelands in 2019 regarding how the bank operated, how it served Gupta’s companies, and whether Gupta was fit to control it.

In March, the BoE forced Wyelands to hand back £210 million (U.S. $291 million) of deposits to around 4,000 savers after concerns emerged over how the bank was financing GFG Alliance, as well as other firms Gupta owned and to which the bank lent money.

It is not just the BoE gunning for Gupta. Last month, the U.K. Serious Fraud Office announced an investigation into suspected fraud, fraudulent trading, and money laundering at GFG Alliance in relation to the company’s financing and conduct of business, including its arrangements with Greensill.