Immigration and Customs Enforcement (ICE) said in a statement they detained about 680 people who were working illegally at the plants. They said they also seized business records as part of a federal criminal investigation.

Some of those detained will be released for “humanitarian reasons” and required to appear in U.S. immigration court, the U.S. Attorney’s Office of the Southern District of Mississippi, which partnered with ICE, said in a statement. Others will be transported to an ICE facility in Jena, Louisiana, it said.

A video released by ICE showed buses arriving at a Canton, Mississippi, processing facility where agents searched workers and checked their identification documents. Some workers had their hands restrained with nylon ties, the video showed.

ICE did not specify the nationalities of the workers arrested. The Mexican Consulate said it was traveling to the area to assist its nationals who might have been involved.

Past large operations to enforce immigration laws at workplaces have included the arrest in 2008 of more than 300 workers at a kosher meatpacking plant in Postville, Iowa.

During the administration of former President Barack Obama, ICE prioritized the arrests of recent border crossers, people who had previously been ordered deported and those seen as a threat to public safety.

President Donald Trump has made cracking down on illegal immigration a centerpiece of his presidency, however, and ICE has stepped up its activities considerably since he took office in January 2017.

ICE said it has made more than 2,300 criminal and administrative arrests related to workplaces in the 2018 fiscal year, which ended in September, compared to just over 300 in the previous year.

Among the facilities targeted in Wednesday’s operation was a Peco Foods processing plant in Canton. On its website, Peco Foods says it is the 8th largest poultry producer in the United States.

Tom Super, spokesman for the National Chicken Council, an industry group, said meat processing companies do their best to hire legal workers.

“The chicken industry uses every tool in the tool box to ensure a legal workforce,” Super said.

Reporting by Kristina Cooke in San Francisco and Mica Rosenberg in New York; additional reporting by Thomas Polansek in Chicago and Lizbeth Diaz in Mexico City; Editing by Sonya Hepinstall