U.S. audit regulators have fined PwC’s affiliate in Mexico for a seemingly brazen failure to observe auditor independence rules.

The Public Company Accounting Oversight Board issued a $100,000 civil penalty to PricewaterhouseCoopers S.C. in Mexico over auditor independence rules tied to an unnamed bank. The PCAOB says the firm accepted an engagement with the bank in 2016 without noticing or considering six of its partners had personal financial relationships with the bank, three of whom had prohibited debtor-creditor relationships either with margin loans or mortgages on a second home. The PCAOB says the firm identified the issues a few months after agreeing to the engagement but took two years to unwind the arrangements that compromised independence.

The PwC affiliate in Mexico is registered with the PCAOB to perform audit work relied on in U.S. capital markets. The firm is the principle auditor for two public companies listed on U.S. exchanges, but it also plays a role in more than 50 other engagements, performing work relied on by other PCAOB-registered firms, according to the PCAOB’s enforcement release.

The PCAOB’s auditor independence rules prohibit audit firms from performing engagements where certain members of their firm and their family members may have a personal interest that could affect auditor judgment. Under PCAOB Rule 3520 on auditor independence and Rule 3526 on communication with audit committees, firms are required to establish independence before accepting engagements, and they are required to assert their independence in communications with audit committees.

The Securities and Exchange Commission also has a separate set of rules requiring auditors to maintain independence from their audit clients. The SEC recently revised its rules to rein in some of the more obscure relationships prohibited that made it difficult for large firms to establish independence on large engagements.

The PCAOB says the PwC firm in Mexico failed to identify its independence issues in advance of the engagement and failed to communicate appropriately with the audit committee. The enforcement release says the firm also continued performing audit work even after identifying the independence violations, audit issuing opinions on the bank’s 2016 and 2017 financial statements while it knew it was not compliant with the requirements.

In a statement, PwC Mexico said it cooperated with the PCAOB’s investigation and is pleased to resolve the matter. “We take our independence obligations seriously and remain committed to compliance with the rules and standards related to independence,” the firm said. “Through our ongoing efforts, PwC Mexico continues to add additional controls to achieve our audit quality objectives and maintain independence and objectivity.”

In addition to the $100,000 penalty, the PCAOB also sanctioned the firm and required it to establish or revise its policies as necessary to prevent future lapses.