Properties linked to British billionaire Sanjeev Gupta's GFG Alliance — the owner of Whyalla's steelworks — have been searched overnight by officers from the UK's Serious Fraud Office.
In a statement, the office said it attended the addresses in England, Scotland and Wales to request documents, including company balance sheets, annual reports and correspondence.
It said it spoke with executives who cooperated with the operation.
Investigators also visited the company's office in Paris and an aluminium smelter in the French city of Dunkirk last week.
GFG operations in Australia include the steelworks in South Australia and the Liberty Bell Bay smelter in Tasmania, as well as Infrabuild steel distribution.
In May last year, the Serious Fraud Office announced it was investigating suspected fraud, fraudulent trading and money laundering in relation to the GFG Alliance, including its financing arrangements with Greensill Capital.
Greensill Capital was a major lender to GFG and collapsed in April 2021.
A GFG Alliance spokesman told ABC News this morning the "low-key visit" by investigators "was an expected step in the process".
"We continue to deny any suggestion of wrongdoing, and we are cooperating fully with the enquiries to help ensure a swift conclusion," he said.
"The enquiries only relate to some of our business in the UK and France, and do not relate to our Australian operations which continue to perform strongly.
"We continue to focus on operating safely and delivering our business plans."
Mr Gupta visited South Australia at the start of the month, announcing an expansion to the company's iron ore processing in Whyalla.
His company bought the Whyalla steelworks in 2017 after the former operator, Arrium, had been in administration for more than a year.
Late last year, GFG Alliance said profit from the Whyalla steelworks had helped it repay creditors and secure a funding agreement to restructure the debt of Mr Gupta's international empire.
Eddie Hughes — the Labor MP for the SA state seat of Giles, which includes Whyalla — said locals had "been through a lot" in recent years, but said the steelworks' "underlying fundamentals" remained strong.
Asked whether he was concerned that the investigation could lead to ramifications for Whyalla, Mr Hughes was sanguine.
"It's still very early days at this stage so let's wait and see, but I know that we will have a future in Whyalla," he said.
"People will look at this, they know that this is the early days of an inquiry, there might be absolutely nothing to it but we'll keep a watching brief.
"There'll always be a degree of anxiety but people in Whyalla know that the steelworks is operating really well at the moment, just cranking out a lot of steel.
"The iron ore mines have generated a lot of cash and the other operations here in Australia — InfraBuild — are all doing incredibly well, so the underlying fundamentals in Australia are very strong indeed, so that gives people confidence that there is going to be a very strong future in Whyalla."
