The U.K. Financial Reporting Council (FRC) has launched an investigation into Deloitte regarding its audits performed at passenger transport company Go-Ahead Group.

The probe, announced Tuesday, will cover the audits of Go-Ahead’s financial statements for the fiscal years ended 2016-21. The investigation will be conducted by the FRC’s Enforcement Division and will not relate to any individuals, the regulator noted.

“We will cooperate fully with the FRC’s investigation,” a spokesperson for Deloitte UK said in an emailed statement. “Deloitte is committed to the highest standards of audit quality.”

Go-Ahead last month announced it received a penalty notice totaling 23.5 million pounds (U.S. $30.7 million) from the U.K. Department for Transport. The fine follows Go-Ahead being stripped of control of its Southeastern rail contract after it was discovered the company improperly retained £25 million (U.S. $32.6 million) of taxpayer money.

Go-Ahead in December admitted to “serious errors” regarding its rail operations and said it apologized to the Department for Transport. The company braced for a potential fine of £30 million (U.S. $39 million) from the agency.

Go-Ahead has referred itself to the Serious Fraud Office, which has yet to announce any investigation.