MORTON, Miss. — Mississippi residents rallied around terrified children left with no parents and migrants locked themselves in their homes for fear of being arrested Thursday, a day after the United States’ largest immigration raid in a decade.

A total of 680 people were arrested in Wednesday’s raids, but more than 300 had been released by Thursday morning with notices to appear before immigration judges, said U.S. Immigration and Customs Enforcement spokesman Bryan Cox.

About 270 were released after being taken to a military hangar where they had been brought, and 30 were released at the plants, Cox said. He did not give a reason except to say that those released at the plants were let go due to “humanitarian factors.”

Those released included 18 juveniles, with the youngest being 14 years old, said Jere Miles, special agent in charge of ICE’s Homeland Security Investigations unit in New Orleans. Workers were assessed before they were released, including for whether they had any young children at home.

A small group seeking information about immigrants caught up in the raids gathered Thursday morning outside one of the targeted companies: the Koch Foods Inc. plant in Morton, a small town of roughly 3,000 people about 40 miles (65 kilometers) east of the capital of Jackson.