German authorities on Tuesday ordered a new lockdown for an entire district -- the first since easing coronavirus restrictions and a major setback for hopes of a swift return to normality.

The move came after a coronavirus outbreak at a slaughterhouse that has infected more than 1,500 workers. "For the first time in Germany, we will return an entire district to the measures that applied several weeks ago," said Armin Laschet, state premier of North Rhine-Westphalia.

He said the lockdown would affect 360,000 people in the district of Guetersloh, and would stay in place until at least June 30. The new outbreak occurred at a slaughterhouse in the town of Rheda-Wiedenbrueck that employs nearly 7,000 people. As of Sunday, 21 people were being treated in hospital, six of them in intensive care.

The outbreak in Germany's most populous state is the biggest since the country began lifting the lockdown in early May. Local authorities across Germany agreed then to pull an "emergency brake" and reimpose social curbs if the infection rate rises above 50 cases per 100,000 residents over a week in a particular district. The rate in Geutersloh has soared well above that, sitting at 263 cases per 100,000 residents on Monday.

The new lockdown means a return to measures first introduced in March, with cinemas, museums, concert halls, bars, gyms, indoor swimming pools and saunas shut down, Laschet said. Schools and kindergartens have also been closed ahead of school holidays which will start this weekend. The move comes as Germany and the rest of the EU begin taking steps towards getting tourism up and running again, with many European borders reopening just last week.

Several planeloads of German tourists have flown to Spain's Mallorca island to take part in a test of plans to reopen the popular destination as the country emerges from its coronavirus lockdown. But the latest flareup in Guetersloh prompted authorities in the German island of Usedom to turn away a couple who had travelled from the affected district.

Under control

Several COVID-19 outbreaks at slaughterhouses, not just in Germany but also in France, have put a spotlight on the working and housing conditions facing the workers -- many of whom come from Romania or Bulgaria.

The German government has responded by banning the use of subcontractors in the meat industry in a bid to curb the controversial practice of companies using middlemen to supply workers from abroad who are more vulnerable to abuses.

But Germany has also seen new coronavirus clusters in residential buildings in Lower Saxony and in Berlin, where 370 families living in high-rise flats were placed under quarantine in one neighbourhood last week. Despite the new outbreaks, the Robert Koch Institute (RKI) disease control centre remained optimistic on Tuesday that the virus remains under control in Germany.

"If we are able to keep the number of cases low the whole time, then we will be able to contain and end outbreaks locally, and that will remain the case," RKI head Lothar Wieler said.

With new infection rates sharply down from highs in March and a death toll significantly lower than those of its neighbours, Germany became the first major EU country to begin easing virus restrictions about seven weeks ago. The government has noted that rules to maintain a minimum distance of 1.5 metres (five feet) as well as requirements to cover up noses and mouths in closed public spaces have helped in the fight against new transmissions.

It is now counting on contact tracing -- both through human trackers as well as through a new app -- to ensure that any new infections are isolated. Chancellor Angela Merkel has repeatedly warned against complacency before a viable vaccine is found.