German authorities in the state of North Rhine-Westphalia have reimposed lockdown restrictions in two districts after a spike in cases, with more than half a million people affected.
One area is home to a meatpacking plant where more than 1,500 workers have tested positive.
State premier Armin Laschet said the "preventative measures" in Gütersloh district would last until 30 June.
Neighbouring Warendorf district has also seen restrictions return.
The state's health minister, Karl-Josef Laumann, announced the second lockdown just hours after the first, saying further measures were needed "in order to protect the population".
It is the first time lockdowns have been reintroduced in Germany since the country began lifting nationwide restrictions in May.
Germany has been praised for its overall response to the pandemic, but there are fears infections are rising again.
Authorities in North Rhine-Westphalia had been among those strongly pushing Chancellor Angela Merkel to ease national restrictions in recent months.
What's happening in North Rhine-Westphalia?
On Tuesday morning, Mr Laschet described the outbreak linked to the Tönnies meatpacking plant, south-west of the city of Gütersloh, as the "biggest infection incident" in the country. Just hours later, health minister Laumann announced that Warendorf would also reimpose restrictions.
In the two districts, bars, museums, cinemas and gyms must all close, and restaurants can only serve meals to take away. Stricter social distancing measures are also back in force, meaning people can only meet one person from outside their own household and it has to be in public.
Schools and nurseries have already been closed in Gütersloh, and those in Warendorf will shut their doors on Thursday.
There is also a mandatory quarantine in place for all employees of the affected Tönnies plant. Three police units have been deployed to enforce the measures, accompanied by aid workers.
Authorities have put up metal fencing around residential buildings where plant staff live and are distributing food to more than 7,000 employees, many of whom are migrants. Translators are on hand to explain the situation.
All operations at the meatpacking site were suspended last Wednesday. A spokesman for the Tönnies Group apologised for the outbreak, though Mr Laschet on Tuesday accused the company of a lack of cooperation.
People are not barred from leaving the two areas under renewed lockdown, but Mr Laschet appealed for local residents "not to travel to other districts".
What's the overall situation in Germany?
Local authorities in Germany have the power to enforce different measures in their areas. Regulations differ from region to region.
This is not the only localised outbreak in the country. A tower block has been placed under quarantine in the central German city of Göttingen, and police were sent to maintain order on Saturday after some residents tried to get out.
Lothar Wieler, head of the nation's public health body - the Robert Koch Institute (RKI) - told reporters on Tuesday the country was at risk of a second wave of infections but said he was optimistic that this could be prevented.
Currently the reproduction rate, or R-number - which indicates how many people one infected person will on average pass the virus on to - in Germany is estimated at 2.76.
The R number must be below one for infection rates to fall but authorities have stressed that outbreaks pushing up R remain localised.
BBC Berlin correspondent Damien McGuinness reports that as Germany's overall infection rate is low, these sudden local outbreaks have a big impact on the national R number. In the past week, 140 local authorities have seen no new cases at all.
Other European countries are also seeing small outbreaks. On Monday the north-eastern Spanish region of Aragón reimposed stricter lockdown measures on about 68,000 residents of Huesca province.
Health minister Salvador Illa said officials were closely monitoring the situation and said it was "on its way to being under control".