A pharmaceutical firm has said it "never had a contract or agreement directly with Wales" to supply coronavirus testing.
First Minister Mark Drakeford had earlier told AMs the Welsh Government did have a deal with Roche.
It emerged on Saturday an agreement to provide 5,000 extra tests a day had collapsed but ministers had refused to name the firm.
Wales is now part of a UK roll-out of testing.
Responding to a question from Plaid Cymru leader Adam Price, Mr Drakeford said: "We did have a deal, it was a deal that we had with Roche."
"We believe that it was a deal that ought to have been honoured.
"We now have access to a supply of tests from a consortium of suppliers that will give us a considerable uplift in testing here in Wales.
"Truthfully, what I believe patients are interested in is that testing will be available, that staff can be tested and go back to work, and some of the detail of how that came about is not, I think, uppermost in the minds of people who need that testing.
"They want to know it's there and is going to be available, and available in greater numbers, and we can be confident of that."
Mr Price said he welcomed the first minister's decision to name Roche as the company involved but said more information was needed.
"We still don't know why the deal collapsed in the first place," he said.
"It is in the public interest that the Welsh Government and Roche tell us what exactly happened to make the agreement fail."
A spokeswoman for Roche Diagnostics said it never had "a contract or agreement directly with Wales to supply testing".
"Our absolute priority and focus at this time is to support the UK government and NHS to scale up testing across the whole of the UK, including in Wales.
"As part of the centralised roll-out of testing, we will continue to speak to colleagues at Public Health Wales to move this forward as quickly as possible."
Stephen Crabb, the Conservative chair of the Welsh Affairs committee,said the reported collapse raised questions about "co-ordination and co-operation between Whitehall and Cardiff Bay in the procurement of tests and other essential equipment".
He has written to Welsh Secretary Simon Hart asking for clarification on what knowledge the UK government had of the deal, whether the company had also been in negotiations with Public Health England and on the steps the UK government was taking to work with the Welsh Government on testing.
"The people of Wales need an urgent assurance that the UK and Welsh governments are working together effectively to ensure all corners of the UK are given their fair share of testing kits," he said.