The corona outbreak in Garmisch-Partenkirchen in Bavaria is said to be due to a US tourist.
The young woman is said to have been in several localities, although she had symptoms, said the spokesman for the district office, Stephan Scharf.
She would be a so-called super spreader.
According to Scharf, 23 people have so far tested positive in an accommodation on the premises of the US armed forces, in which she had stayed.
Overall, the number of new infections was 33 in one day.
The seven-day incidence was 54 and thus above the critical mark of 50 new infections per 100,000 inhabitants in seven days.
The district office then imposed restrictions on the market town.
For example, only five people are allowed to meet there in public.
According to the district office, the 26-year-old traveled to Germany at the beginning of September or the end of August and is said to have been in the Garmisch-Partenkirchen nightlife for several days.
It is still unclear whether she brought the virus with her from the USA and possibly disregarded quarantine rules.