Reports from the Departments of Justice and Homeland Security said that the worksite enforcement operation, which took place at multiple food processing locations, netted 680 arrests in what the DOJ described as the "largest single-state worksite enforcement action" in USA history.
It's unclear whether the raids were intentionally scheduled for the same day as Trump's visit to El Paso. The suspected gunman was linked to an online screed about a "Hispanic invasion", in language that echoed Donald Trump's rhetoric on immigration. Those arrested were taken to the military hangar to be processed for immigration violations.
He did not say why they were let go except to say those released at the plants had been let go due to "humanitarian factors".
A tearful 13-year-old boy was seen waving at his worker mother, as he stood beside his father. Some employees tried to flee on foot but were captured in the parking lot.
ICE agents searched the plant, asking employees for identification.
The companies who hired illegal workers will be scrutinized for tax, document and wage fraud, Albence said.
Koch Foods didn't respond to telephone calls and emails seeking comment.
USA immigration authorities arrested about 680 undocumented immigrants at seven sites in six different cities in MS on Wednesday.
The largest single state immigration enforcement operation in the USA history took place on August 7.
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Protesters were joined by teachers, security workers and some 2,300 aviation workers, resulting in 224 flight cancellations . In several locations, they used flash grenades and tear-gas against black-clad protesters wearing face masks.
"Our enforcement operations are being done on a racially neutral basis", Albence said.
About 600 ICE agents arrived at the chicken processing plants, owned by five different companies, in the towns of Bay Springs, Canton, Carthage, Morton, Pelahatchie and Sebastopol.
Such large raids were common under President George W. Bush, most notably at a kosher meatpacking plant in tiny Postville, Iowa, in 2008. Barack Obama avoided them, limiting his workplace immigration efforts to low-profile audits that were done outside of public view.
In Morton, 40 miles east off capital Jackson, workers filled three buses at a Koch Foods plant.
Children have been left abandoned and homeless, crying in the streets of cities across MS after a massive raid by ICE. Last year, the administration hit a landscaping company near Toledo, Ohio, and a meatpacking plant in eastern Tennessee.
Forbes ranks it as the 135th largest privately held company in the US, with an estimated $3.2 billion in annual revenue.
Agents who arrived at the Morton plant passed a chain-link fence with a sign that said the company was hiring. Mike Hurst, the USA attorney for MS, was at the scene. Workers' wrists were tied with plastic bands and they deposited personal belongings in clear plastic bags. Agents collected the bags before they boarded buses.
The Rev. Mike O'Brien, pastor of Sacred Heart of Jesus Catholic Church in Canton, said he waited outside the Peco Foods plant in the city until 4 a.m. Thursday for workers returning by bus. 'Without them here, how will you get your chicken?'