The timing of a string of immigration enforcement raids at Mississippi food processing plants last week was "unfortunate," but the actions had been planned for over a year, the top U.S. Homeland Security official said on Sunday.

Kevin McAleenan, acting secretary of the Department of Homeland Security, spoke about the actions by U.S. Immigration and Customs Enforcement, or ICE, on NBC's "Meet the Press."

About 680 immigrant workers were arrested Aug. 7 at seven facilities in the southern state, the largest workplace raid in about a decade, U.S. authorities said. Videos and images in news reports and on social media showed children whose migrant parents were detained pleading for their release.

Asked whether he wished the raids hadn't happened last week after a mass shooting the previous weekend in El Paso, Texas, targeting Hispanic people, McAleenan said "the timing was unfortunate."

Still, he said the operation, more than a year in the planning, "was done with sensitivity."

"ICE took great pains to make sure there were no child-dependent care issues that were ignored," McAleenan said on NBC.

Also on "Meet the Press," Sen. Kamala Harris of California, a 2020 Democratic presidential hopeful, said the immigration raids were part of a "campaign of terror" by President Donald Trump's administration to make Hispanic Americans "afraid."

The ICE raids have been criticized by other Democratic lawmakers, including Rep. Bennie Thompson of Mississippi, head of the House Homeland Security Committee. Thompson said in a statement that ICE seemed to have ignored internal guidelines requiring it to minimize the impact on children affected by such measures.

"The Department of Homeland Security's leadership has a responsibility to understand the consequences of its actions, and I seriously question why they continue to target migrant families in this way," Thompson said.