LOS ANGELES — Homeland Security officers visited two Los Angeles public elementary schools this week to do a welfare check on migrant children, not for immigration enforcement, the department said Friday.

The officers were denied access by both principals. The department’s explanation followed harsh criticism by Superintendent Alberto Carvalho of the Los Angeles Unified School District, who said the agents lied to school staff that they had been authorized by the children’s parents and caretakers to go to their schools.

“We have confirmed that that is a falsehood,” Carvalho said at a news conference on Thursday. “We’ve spoken with the caretakers of these children, in some cases parents, and they deny any interaction with these entities, and certainly deny providing authorization for these individuals to have any contact with these children at the school.”

President Donald Trump’s immigration policies have vastly expanded who is eligible for deportation and lifted a ban on immigration enforcement in schools. In Chicago in January, a school mistakenly said federal immigration authorities had come to campus. Officials later said it was officials from the U.S. Secret Service investigating a threat, but the false alarm raised fears among immigrant communities.

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The Department of Homeland Security oversees U.S. Immigration and Customs Enforcement, but ICE agents were not the officers sent to the schools.

DHS stated in an email to The Associated Press that agents with its Homeland Security Investigations agency “were at these schools conducting wellness checks on children who arrived unaccompanied at the border. This had nothing to do with immigration enforcement.”

Homeland Security Investigations conducts criminal investigations into drugs and arms smuggling, cyber crime, human trafficking and child exploitation, among other things.

It added that “DHS is leading efforts to conduct welfare checks on these children to ensure that they are safe and not being exploited, abused, and sex trafficked.”

Employees of Los Angeles Unified School District, the nation’s second-largest district, were trained months ago in anticipation of arrivals by federal agents to campuses, Carvalho said.

Four federal officers arrived Monday morning to Russell Elementary and identified themselves as Homeland Security agents, Carvalho said. They then asked about four students ranging from first-graders to sixth-graders.

The agents told the principal repeatedly that this was not an immigration enforcement operation, federal officials said. They were told they would need a court order.

Two hours later, three Homeland Security agents arrived to Lillian Street Elementary and asked about a sixth grader, the superintendent said.

The agents, according to federal officials, went to Lillian to confirm the residence and verify the safety of a migrant child who arrived to the border unaccompanied and were told by the principal that they would need a warrant.

Carvalho said after asking to see the identifications of the agents, the principals at each school contacted the district’s legal department, which sent representatives and dispatched school board police to the campuses. The federal officers then got in their vehicles and left.

“I am proud of these principals. I am proud of our workforce. I am proud of the clerical staff in the front office for they did exactly what we trained them to do,” Carvalho said.

At one school, agents tried to insist that they have the authority to be on campus, which Carvalho said was incorrect.

“I’m still mystified as to how a first, second, third, fourth or sixth grader would pose any type of risk to the national security of our nation that would require Homeland Security to deploy its agents to two elementary schools,” he said.

Carvalho said the actions add to the fear already being felt in immigrant communities and that his district will not be intimidated.

“Schools are not places of fear,” he said.