SydPath, an Australian-based lab, sent hundreds of patients the wrong test results, due to a "data processing error," it said in a statement.
The lab announced in a statement Monday that a total of 995 people, who had taken COVID- tests on Dec. 22, Dec. 23 and Dec. 24 had received text messages that their test results were negative when the results had not yet been determined.
Of those 995 people, 486 people had actually tested positive.
This comes after the lab announced on Sunday it had told more than 400 people their results were negative when they were positive.
This error comes as the country sees the number of COVID-19 cases surge. On Tuesday, Australia reported 11,260 new positive cases, bringing its cumulative number of active COVID-19 cases to 323,285, according to the government's Department of Health.
The lab, a part of St. Vincent's Hospital Sydney, established an emergency response team to "rectify the issue as soon as possible," according to its website, characterizing the mistake as a "clerical error."
Those impacted had taken tests at any of the lab's clinics.
SydPath said it will reduce the number of tests it processes "to ensure the volume remains within our capacity," it said in the statement.
The lab said it reached out to those people and will update them with their correct results. It advised anyone impacted to self isolate until they are contacted with their correct results, according to its website.
SydPath did not immediately respond to ABC News' Request for comment.