The Serious Fraud Office has visited the offices of Sanjeev Gupta’s Liberty Steel demanding information.
It comes almost a year after the SFO launched an investigation into suspected fraud and money laundering by parent firm GFG Alliance, which has thousands of staff in the UK.
The SFO has confirmed that teams from the organisation visited company offices on Wednesday morning to request documents including company balance sheets, annual reports and correspondence related to the investigation.
It is understood a number of sites were visited across England, Scotland and Wales.
A spokeswoman for the SFO said: “Investigators spoke with executives at multiple addresses, who co-operated with the operation.
“As the investigation is ongoing, the SFO can provide no further comment.”
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 raided the Paris offices of GFG Alliance on Wednesday in its own probe of the tycoon’s business empire.
A spokesman for GFG Alliance declined to comment.
In an internal memo to employees, staff at the company were told: “We will comply with the information request orders and will continue to cooperate fully in all manners.
“We have in place very strict information and document preservation policies which we implemented prior to the SFO announcement.
“I would like to remind you again to please read and observe the attached policy which is mandatory for all employees and contractors.
“We appreciate these enquiries can be disruptive and concerning for employees and stakeholders.
“However, we are encouraged that the investigation is now progressing and is moving closer to a conclusion.”