The Financial Reporting Council, which regulates the accounting industry, said it would be investigating accounts signed off by King and King for four Liberty Steel businesses which include sites in the Black Country.
Offices of Liberty Steel faced visits from Serious Fraud Office investigators last week as part of a probe into suspected fraud and money laundering by parent firm GFG Alliance.
The FRC said it would be combing through accounts relating to Liberty Speciality Steels Limited, Alvance British Aluminium Limited (formerly Liberty Aluminium Lochaber Ltd) and Liberty Steel Newport Limited for the year ended March 31, 2019.
It will also look at Liberty Performance Steels Limited statements for the year ended March 31, 2020.
Last month Liberty Steel UK revealed it is set to get rid of 207 jobs, including 45 at its performance steels site in Albion Road, West Bromwich.
The company, which has sold its Kidderminster aluminium works, also has Bright Bar at Wednesbury.
Mr Gupta was once lauded as the "saviour of steel" for rescuing factories, but has come under heavy scrutiny amid accusations of potentially fraudulent trading after his main lender, Greensill Capital, collapsed a year ago.
GFG used so-called supply chain finance services offered by Greensill.
This meant that if GFG sold a product to a different company, it could send the invoice to Greensill and be paid right away, rather than having to wait potentially months for the customer to pay its bills.
Bringing in money this way can be useful for companies with tight cash flows.
However, how Greensill and GFG did business together is being investigated by the fraud investigators.
It comes after French police visited the Paris offices of GFG Alliance on Wednesday in its own probe of the tycoon's business empire.