More than 300 workers from AgriProcessors kosher meat plant in Postville, Iowa, were arrested Monday after an immigration raid. The workers were suspected of being in the U.S illegally or of having participated in identity theft.

Agents from U.S Immigration and Customs Enforcement had warrants for fraudulent use of others' Social Security numbers in connection with their employment at the plant. According to USA Today, the plant had 800 to 900 workers, many of them being from Mexico, Russia, Ukraine and elsewhere.

Nathaniel Popper, a journalist who has written about AgriProcessors for The Jewish Daily Forward, said that the raid could have an effect on the supply of kosher meat.

“This could have a big impact on the supply of kosher meat in America. Over the next several days, that’s going to be the big question for people in the Jewish community who keep kosher,” said Popper in an interview, as USA Today reported.

The plant was temporarily shut.

According to the affidavit, the investigators were warned about a methamphetamine laboratory that had operated in the plant from a former plant supervisor.

Authorities said the number of arrests was expected to increase, perhaps even double, as the investigation continued.

Matt M. Dummermuth, the United States attorney for the Northern District of Iowa, called the raid “the largest operation of its type ever in Iowa.”

This raid had been planned for months and this was not the first spotlight for the plant. In 2004, after an animal rights group secretly documented workers cutting the throats of living steers and letting them bleed to death, the plant was asked to change its slaughtering methods.

According to the New York Times, the AgriProcessors plant is northeast Iowa's largest employer and provides 60 percent of the kosher retail meat and 40 percent of the kosher poultry nationally.