Magnus Heunicke said that it was still not known whether the person was infectious at the time they took part i the demonstration, but he called on all who were present to get tested as soon as possible.
“We do not know if the person who has been tested has been infected at the demonstration or has infected others at the demonstration,” he said.
“That is why it is crucial that the many participants in the demonstration get themselves tested.”
The demonstration, called “We can't breathe” or “Black Lives Matter” on June 7 drew as many as 15,000 people and was so crowded that it was impossible for most present to keep to social distancing guidelines.
“It was a very, very big demonstration, with 15,000 attending, some of them standing close together,” Heunicke said.
Those who attended the protest with a NemID should book at test on www.coronaprover.dk whether they are experiencing symptoms or not, he added. Those who do experience symptoms should instead contact their doctor.
Anette Lykke Petri, Director of the Danish Patient Safety Authority, said that the person who had tested positive could give little information about where she had been in the protest, or who she had met.
“That's why we're really putting on the armbands and safety harnesses,” she said. “Because it was such a large crowd which was close together for such a long period of time.”
There have been demonstrations across the world in the wake of the death of George Floyd, a black American, during an arrest in Minneapolis a few weeks ago.
Black Lives Matter Denmark is set to hold another demonstration as soon as this Thursday.
A poll by Voxmeter for Ritzau, reported on Tuesday, found that 63 percent of respondents wanted to ban big demonstrations.