Previous reports said about at least 400 employees had been infected.
According to Westfalen Blatt, by Wednesday evening the results of 983 COVID-19 tests among the plant's employees were received, including 657 that were positive.
The plant is currently closed and the authorities are reportedly planning to keep it shut down for 10-14 days.
On Wednesday, the media reported that 7,000 people were quarantined due to the outbreak. All schools and kindergartens in the area were closed as a precaution.
Germany has seen several new COVID-19 outbreaks occur throughout May at meat factories across the country. In particular, 109 COVID-19 cases were recently detected in a slaughterhouse of the Segeberg district in the northern state of Schleswig-Holstein and 200 cases at a meat processing plant in the Coesfeld town in the state of North Rhine-Westphalia. Both have large groups of seasonal workers.