Matthew Albence, the agency’s acting director, described the operation as “racially neutral” and based on evidence of illegal residency.
Most of the detained staff were Latino.
Their arrests came on the same day the president visited El Paso, following a massacre there by a gunman who allegedly posted an anti-immigrant screed before the attack.
The agenda claimed the shooting, which left at least 22 people dead, was a response to the “Hispanic invasion of Texas”.
Bernie Sanders said the Mississippi raids were “evil”.
“Days after immigrants were gunned down in El Paso, Trump is continuing the attacks on immigrant families,” he said on Thursday.
“Our job is to reject Trump’s racist agenda, end the terror inflicted on immigrant communities and bring families together, not tear them apart.”
Beto O’Rourke and Julian Castro also criticised the raids.
“Only days after a massacre committed with the express purpose of targeting immigrants, Trump conducted the largest raid of his presidency,” said Mr O’Rourke, a former congressman who used to represent El Paso.
“Six hundred and 80 human beings arrested, including the mother of a 13-year-old, who waved goodbye as she was taken from him. The cruelty knows no bounds.”
The child Mr O’Rourke referred to was caught up in a raid at a Koch Foods plant in Morton, east of the city of Jackson.
He reportedly waved goodbye to his mother, who is from Guatemala, while standing beside his father.
“On a day when President Trump is supposed to be embracing a grieving community and celebrating our American diversity in El Paso, his administration is instead stoking fear by conducting massive immigration raids in Mississippi,” said Joe Biden, the former vice president, also a Democratic candidate for the 2020 elections.
“He is morally unfit to lead this country.”
The raids were “the largest single state immigration enforcement operation in [US] history”, according to Mike Hurst, US attorney for the southern district of Mississippi.
Staff at meat processing plants are frequent targets for ICE officers.
In December 2006 officials arrested 1,282 people in raids at Swift & Company plants across six different states.
And in 2008 ICE conducted the Postville raid, which saw 389 people arrested at one northern Iowa meat processing plant.
The Postville operation remains the largest single-workplace raid in US history, according to NBC News.
The timing of the Mississippi raids has triggered further anger against the president, who is facing increasing pressure about his rhetoric.
“This is a long-term operation that’s been going on,” Mr Albence said, when asked about the raid coinciding with the El Paso visit.
“Trump uses dehumanising terms like ‘invasion’ to justify an agenda that separates families and targets communities like Morton, Mississippi,” said Julian Castro, a Democratic presidential primary candidate.
“It’s time to break up ICE.”
Additional reporting by agencies
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