A team of corporate investigators has been hired by the assembly government to see if the NHS has been overcharged for drugs, BBC Wales has learnt.
The investigators will look at the drugs bill for Wales' NHS
Ministers want to find out if hundreds of thousands of pounds for a range of prescription drugs could be recovered.
The investigation comes as the Serious Fraud Office has charged a number of firms and individuals over drugs sales.
The assembly government said it had hired investigators Kroll, on what it called an "invest-to-save" basis.
The corporate investigators will examine whether an alleged cartel of companies overcharged Wales' health service for antibiotics and the anti-clotting drug warfarin.
These involve medicines which are now produced generically and are "off patent".
The Department of Health in England has already reached settlements worth more than £30m from a number of firms, without the companies admitting guilt.
It is thought the assembly government hopes to claw back some of the money it has paid in a similar way to pharmaceutical firms.
The Serious Fraud Office has alleged a number of companies and individuals colluded to overcharge the health service for the drugs between 1996 and 2000.
Jonathan Morgan AM, shadow health minister, said the assembly government was right to try to reclaim any lost money.
"If money has been spent on products that were over-charged then clearly that money could have been spent on something else within the NHS," he said.
But he added: "We have to be certain that we're going to reclaim more than we're actually spending out in firms' costs."
Jenny Randerson AM, Liberal Democrat health spokesperson, said: "Any initiative that will deliver more money to frontline NHS services deserves all of our support.
"However, questions must be asked about how loose financial controls could have enabled such a problem to occur."