The Verknipt festival, which attracted about 20,000 visitors, was one of the first after the country relaxed its COVID-19 measures on June 26, local media RTVUtrecht reported.
Before entry, visitors were asked to prove that they had been vaccinated, had recovered from COVID-19 recently, or had tested negative for COVID-19.
Posts from the festival show attendees in close proximity, as can be seen in this tweet from the Mayor of Utrecht Sharon Dijksma, who went on July 3.
On Monday, Dutch Prime Minister Mark Rutte apologized for lifting restrictions too soon, calling it a "miscalculation," Euronews reported.
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"What we thought was possible turned out to be wrong in practice. We made a miscalculation, we are disappointed about it and we apologise," he said.
The government reimposed restrictions on nightlife two weeks after lifting them, and canceled all event with large crowds until August 14, the Irish Times reported.
The figure was five times the number reported the previous week. Of the infections that could be traced back to the source, 37% happened in the hospitality industry, the country's institute of public health found, ABC News reported.
Late last month, 180 people were infected at a "covid-free" party attended by 800 people in a nightclub in Enschede, in the eastern Netherlands, Insider's Mia Jankowicz reported.
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Daily new confirmed COVID-19 cases in the Netherlands, as of July 14.
Our World In Data
In spite of the rise in cases, COVID-19 hospitalizations stayed low, with 60 new hospital admissions on the week of July 6, of which just 12 required intensive care, according to official data.
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