A Homeland Security officer guards some of the 680 suspected undocumented migrants detained in Mississippi after Immigration and Customs Enforcement officers raided several slaughterhouses. — AFP Photo

MIAMI — The Trump administration hailed a large drop in migrant border crossings on Thursday but found itself under attack over a massive sweep of long-resident undocumented immigrants working in several Mississippi slaughterhouses.

Detentions on the southern US border plunged for the second straight month in July after a deal with Mexico to block Central American migrants, the Department of Homeland Security announced on Thursday.

US Border Patrol agents detained or blocked 82,049 migrants at the frontier with Mexico last month, down from 104,367 in June and a 13-year peak of 144,266 in May.

DHS credited a deal with Mexico in June to stem the flow of migrants traveling northward to the United States from Central America -- mainly Guatemala, Honduras and El Salvador -- as well as cooperation by the three in cracking down on migrant smuggling groups.

But the success of the border crackdown was clouded by criticism of the Immigration and Customs Enforcement agency for its workplace raids in Mississippi on Wednesday that rounded up some 680 migrants, many of them longtime US residents, while leaving their children to fend for themselves.

The largest single-state immigration raids in US history targeted seven food processing plants in the southern state, an industry long known to employ undocumented migrants as inexpensive labor.

"They have to follow our laws, they have to abide by our rules, they have to come here legally or they shouldn't come here at all," Mike Hurst, the US attorney for the southern district of Mississippi, said.

But Chokwe Antar Lumumba, the mayor of Jackson, the state capital, blasted the raids and called on local churches to provide migrants sanctuary from authorities.

"The ICE raids are both dehumanizing and ineffective as a tactic for protecting citizens from potential harm," he said.

The American Civil Liberties Union accused the administration of "terrorizing" migrant communities.

"We are deeply concerned that the raids have separated Mississippians' families, disrupted our local economy, and diverted our state's limited resources to support Trump's mass deportation agenda," said Joshua Tom, interim executive director of the ACLU of Mississippi.

"Local law enforcement should refuse to cooperate with the president's anti-immigrant policies."

'I need my mommy'

Local television broadcast tearful scenes of children returning from school on Wednesday to find out their parents had been taken away by authorities.

"I need my dad and mommy," 11-year-old Magdalena Gomez Gregorio told WJTV. "My dad didn't do anything, he's not a criminal."

Neighbor Christina Peralta said the girl's mother had been in the country for 15 years and had no record.

Peralta was taking care of two boys whose mother also was arrested.

"They've been crying all day since they got home from school," she said.

ICE, which has come under fire before for arresting undocumented migrants without providing for their children, said it had allowed detainees on Wednesday to contact their families and make arrangements for the children.

Around 300 of the 680 detainees had been released by Thursday after being processed by authorities. In a statement, the office of the federal prosecutor in Jackson said that if two parents were swept up in the raid, one would be released to care for their children.

"Based on these procedures, it is believed that all children were with at least one of their parents as of last night," it said.

Several Democratic politicians running for president attacked Trump's policies as immoral.

"This is inhumane and will have devastating effects on the children that are left behind," said Senator Elizabeth Warren, one of the candidates. — AFP