Officials said 45 cases of COVID-19 have been identified by Tuesday evening among employees of a catering company in the Upper Bavarian town of Gilching.

Further testing among those sharing accommodation with the workers was underway on Wednesday, along with a tracking operation for other contacts of those who were infected.

Among the facilities refugee homes affected was one in nearby Hechendorf, where 10 of the employees who tested positive were living. That center and three others have been closed, and residents placed under a 14-day quarantine.

"The important thing now is to break the chain of infection," a spokeswoman for the municipality of Starnberg told the Süddeutsche Zeitung newspaper.

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Municipality leaders say a more general lockdown for the wider municipality is not imminent.

"We are currently a long way from that," said district authority head Stefan Frey. Lockdowns across such wide areas should only take place where an outbreak could not be tracked specifically he said.

"This is not currently the case with us," said Frey, adding that the chain of infection appeared to have been established and the SARS-CoV-2 virus prevented from spreading.

"To keep it that way, we will do everything possible and act strictly and consistently," said Frey.

Catering firm Apetito said it was investigating the cause of the outbreak.

"As far as we know, all employees at the company have observed the hygiene practices of social distancing and wearing mouth and nose protection."

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The catering plant at Gilching supplies Munich's Ludwig-Maximilians-University hospital with more than 6,000 meals per day for staff and patients.

Officials from Germany's Federal Insititute for Risk Assessment said any transmission of the virus through pre-prepared food is very unlikely.

The infections were discovered after one resident of the home in Hechendorf visited the doctor with mild symptoms of infection.

Germany's first coronavirus cases nationwide were diagnosed in Starnberg in February after a visiting Chinese employee of the auto parts firm Webasto passed the virus on to a coworker.