A fake letter claiming to be from Greg Hunt was allegedly used by a company attempting to illegally import unapproved rapid antigen tests.
Limited supply has seen a scramble for rapid COVID-19 tests across the country, with many pharmacies and retailers unable to keep up with skyrocketing demand.
It was only legal to supply tests listed on the Australian Register of Therapeutic Goods without an exemption, none of which have been approved.
But the Therapeutic Goods Administration on Friday revealed it was working with the Australian Federal Police to investigate "false documentation" provided by a company looking to circumvent the strict regulations.
"The letter, claimed to have been issued by Minister Hunt, appears to provide a NSW-based company with an exemption ... prior to importation and supply in Australia," its statement read.
The AFP spokesperson also confirmed inquiries into the matter were ongoing.
"The AFP can confirm it has received a report from the Therapeutic Goods Administration containing allegations that false documentation was used to support the illegal importation and supply of unapproved rapid antigen tests," it said.
"No further comment can be made at this time."
The nature of the company, or when it provided the document, was unclear.
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It comes as Mr Hunt revealed demand for the government's concessional rapid antigen test program, which began this week, had far exceeded initial expectations.
After facing pressure to make rapid tests free as they were in many countries, the federal government in January announced concession card holders would receive a limited number without charge.
Mr Hunt said around 380,000 people had already signed up to the program, which had delivered nearly 1.7 million rapid tests so far.
"The numbers of participating pharmacies are now triple what we had expected at this stage ... and the number of concession cardholders is well over double what we had expected, in terms of both the number of individuals and the tests that have been dispensed for free," he said.