It is P4 Halland that has taken part in a report and email conversations between Region Halland and an external test lab.
They say that 13 people in southern Sweden were affected by the error, seven from Halland, two from Skåne and four from Kalmar.
The reason is that the equipment that evaluates the PCR tests was not sufficiently cleaned.
The deficiency was discovered in April.
- We can not rule out that there are several false positive answers, but as we now know, there are no more incorrect tests, says Johanna Wiechel-Steier, communications director at Region Halland to the radio.
If the people tested were really infected, it is not possible to say when the samples have been discarded.