President Donald Trump claimed success in a widely publicized effort to raid and deport undocumented immigrants, saying Monday that planned sweeps targetingundocumented immigrants in several major U.S. cities had been under way several days prior.

"It was a very successful deal," Trump told reporters at the White House on Monday morning, saying they had taken place on Sunday. "You just didn't know about it," he added.

Trump didn't include any additional details about the highly publicized operations, refusing to say how many people U.S. Immigration and Customs Enforcement officers had arrested, or where those operations took place.

His remarks contradicted reports from local elected officials, migrant advocacy and legal groups monitoring for activity in their respective cities. They reported seeing little to no activity over the weekend, except for two failed Saturday raids in New York City.

PHOENIX RAIDS:No ICE raids in Phoenix area, but families prepare for the worst

On Monday, details emerged about successful sweeps taking place in some of the targeted cities.

Federal agents descended onto Houston on Monday morning and over the weekend as part of the nationwide sweeps, according to advocates and eyewitnesses.

Cesar Espinosa, executive director of immigrant rights group FIEL Houston, said ICE officers arrested six people during raids on El Paraiso Apartments in southwestern Houston. At least four others were detained Saturday during an earlier sweep.

The aggressive nature of the raids — done in morning light, not under cover of darkness, with agents banging on doors — made Espinosa think it was part of the nationwide sweep of undocumented immigrants designed to intimidate and discourage other migrants from coming to the U.S. without proper documentation.

Many residents didn’t open their doors to the agents if they didn’t have a warrant, which Espinosa called a sign that the group’s outreach and know-your-rights forums are working.

“We know that people are being more prepared now. We know that people are asserting their rights,” Espinosa said. “There’s a lot more increased fear, but at the same time people are reacting better.”

ICE arrests in Houston, Texas

Kalyin Garcia, 19, was coming out of her apartment at El Paraiso just before 7 a.m. Monday to drive her mom to work when a team of agents walked by. The three men and a woman were wearing black shirts or camouflage with the letters “ICE” emblazoned across a black vest. One was studying a sheet of paper. “Good morning,” one of them told Garcia.

Garcia, who is a U.S. citizen, as is her mom, told her mom to go back inside the apartment and get her documents, in case they came for her. Later, Garcia saw the agents banging on a neighbor’s door. “Open the door!” they yelled. No one answered. Garcia snapped a photo of the team on her smart phone and posted it to Facebook to alert neighbors and advocates.

“I got scared,” she said. “I don’t know what could happen. He comes out and they could take him. I was scared for them.”

Odilia Leigh, the complex's property manager, said she started getting phone calls from panicked tenants as soon as she arrived at the office around 8:30 a.m. Monday. Several tenants told them they had seen ICE agents on the property and at neighboring apartment complexes, banging on doors.

She told them not to open the door to anyone and ordered the maintenance worker to make sure public-access gates to the property were all locked. She said she knew the agents were likely U.S. law enforcement involved in the nationwide sweep — but her tenants’ safety and state of mind come first, she said.

Leigh said the apartment complex does background checks on tenants and she was confident there were no criminals staying there.

“These are good people, families,” she said. “I want them to feel safe.”

In a written statement, an ICE spokeswoman said that "due to law-enforcement sensitivities and the safety and security of U.S. Immigration and Customs Enforcement personnel, the agency will not offer specific details related to enforcement operations."

The statement went on to say that the arrests would prioritize undocumented immigrants with criminal backgrounds.

At a news conference with consular officials in the United States, Mexico's Foreign Minister Marcelo Ebrard said they had no reports of Mexican citizens arrested in the past few days.

"We don't have an increase in the number of Mexicans detained in the U.S., nor an increase in the number of deportees. But that doesn't mean that it won't happen in the coming days," Ebrard said.

Immigration officials had said previously that the raids planned for this week would target nearly 2,000 migrants that who had recently arrived in the country and had outstanding deportation orders.

But they also warned about the possibility of "collateral arrests," the detention of other individuals in the country illegally caught up in the raids.

USA TODAY's David Jackson contributed to this article.

Have any news tips or story ideas about the U.S.-Mexico border? Reach the reporter at rafael.carranza@arizonarepublic.com, or follow him on Twitter at @RafaelCarranza.

Support local journalism. Subscribe to azcentral.com today.