Federal agents raided several companies across Mississippi on Wednesday, rounding up hundreds of immigrant workers in what federal officials said might be the largest worksite enforcement action ever in a single state.

In a coordinated sting, more than 600 agents from Immigration and Customs Enforcement showed up at the sites with federal warrants that allowed them to search the premises. About 680 immigrants who were believed to be working without legal documentation were apprehended and taken away on buses.

Lindsay Williams, a spokesman for the agency, said the federal agents executed the search warrants in conjunction with the United States Attorney’s Office for the Southern District of Mississippi.

The operation was the culmination of a yearlong investigation, and it unfolded just hours before President Trump — who has made illegal immigration a trademark issue and who recently vowed to deport millions of undocumented immigrants — arrived in El Paso, a majority Latino city on the Mexico border where 22 people were killed over the weekend in an attack that federal authorities are investigating as an act of domestic terrorism.