U.S. Border Patrol officials in Arizona said they have started releasing migrant families from their custody into the streets of Yuma because processing centers can't cope with the large numbers of arriving families and minors.

Community groups in the Yuma area have set up temporary facilities to house the families and to provide food and shelter while they assist migrants with travel plans to leave the border city.

The Border Patrol issued a statement Thursday announcing its decision, which followed the lead of officials in the Rio Grande Valley in south Texas, who last week began releasing families from their custody.

"U.S. Border Patrol processing centers are not designed to house the current numbers of families and small children that we are encountering," the Border Patrol's Yuma sector said in a written statement. "Due to capacity issues at our stations and the ongoing humanitarian crisis nationwide, Border Patrol has begun identifying detainees for potential release in Yuma with a notice to appear for their immigration hearings."

In a news conference on Thursday afternoon, Carl Landrum, the Yuma sector's deputy chief, explained Border Patrol made the decision as a dramatic surge in migrant families and minors overwhelmed their resources and holding spaces.

According to the latest government statistics, in the first five months of the fiscal year, agents in Yuma have apprehended 17,578 migrants traveling as a family. By contrast, in that same time period last year, they encountered 5,319 migrants. That's a 330 percent increase and does not include rising numbers of unaccompanied minors and other single-adult migrants.

The sector is on track to apprehend a total of 60,000 migrants, Landrum said. Those are the highest levels since 2007, when the installation of additional border fencing began to reduce the number of migrants crossing through Yuma.

Landrum added the sector has the capacity to hold 400 migrants at its processing center and three patrol stations in the sector, but that the facilities were designed to hold single adults for short periods.

With a vast majority of apprehensions consisting of Central American families and minors claiming asylum, they cannot be deported right away, so they remain in custody longer.

That's why they decided to begin releasing families, he said. Those eligible for release are migrant families who are released into the custody of relatives living in the United States and who have undergone medical screenings.

“It’ll continue right now, there is not an end date established," he said about the releases in Yuma. "Until we can actually maintain the capacity ... We've been overcapacity about 200 percent for the past two years.”

Temporary facilities to house migrants

Yuma Mayor Doug Nicholls also talked about the impact of these releases during Thursday's news conference. He said the Border Patrol could release up to 200 migrants into his community each day.

The decision prompted nonprofit groups in the Yuma area to "create a plan of action for a humanitarian response,"' he said. That plan included opening temporary facilities to house migrants and to help them arrange for transportation after their release.

But that effort has limitations, Nicholls said.

“The full capacity of the (nonprofit groups) in Yuma cannot address the full volume of migrants, should the volume increase as projected,” he warned.

Normally, once the Border Patrol apprehends migrants, the agency is legally obligated to detain them for no more than 72 hours and then transfer them into the custody of Immigration and Customs Enforcement.

Immigration officials either would keep them in detention for longer periods of time, or, in the case of migrant families, release them into the custody of relatives living in the United States and give them a notice to appear in court later.

But in the past few months, the drastic surge of migrant families in southwestern Arizona has overwhelmed border agents as well as immigration officers.

MORE: ICE dropped off 300 migrants in Phoenix. Will the city help?

"The sheer volume of family units (FAMU) crossing the border has overwhelmed ICE’s limited transportation resources," spokeswoman Yasmeen Pitts O'Keefe said in a statement. "Combined with a requirement to detain these individuals for no more than 20 days, the agency has no option but to expeditiously arrange for their release."

O'Keefe confirmed that even though the Border Patrol has begun to release some families, immigration officials still are taking other migrant families into their custody.

In October, ICE officials in Arizona made a similar decision when they announced they no longer would help arrange travel plans for migrant families released into the care of relatives.

ICE officials began releasing families into the streets of Yuma, overwhelming the only shelter for migrants in the city. Catholic Community Services of Southern Arizona stepped in and began housing migrants at a hotel while it helped arrange transportation, despite limited options.

ICE's decision was met with backlash from local elected and community officials. Then-Sen. Jon Kyl, R-Ariz., also intervened, sending a letter to Homeland Security Secretary Kirstjen Nielsen to pressure them for a better solution.

She visited the Yuma area in late October. After her visit, ICE agreed to transport those families to Phoenix and Tucson instead.

Yuma mayor asks for help

Yuma Mayor Nicholls said he also reached out to fellow Republicans, including Gov. Doug Ducey and U.S. Sen. Martha McSally, to pressure the federal government to take action to mitigate these releases.

That could include allocating additional resources to ICE and Border Patrol, as well as "a FEMA-type response to handle the release of individuals and to provide judges to help facilitate legal proceedings that would reduce the flow of migrants," Nicholls said.

On Wednesday, McSally sent a letter to Homeland Security Secretary Kirstjen Nielsen expressing her concern about the release of families with little advance warning in Yuma, Phoenix and Tucson.

"People in Phoenix, Yuma and throughout Arizona are facing massive financial, public-safety, and humanitarian costs from an immigration crisis that they had no part in creating," she said in the letter. "We need to do better to reduce the burden imposed on them."

In an interview with Phoenix radio station KTAR-FM, Ducey also criticized the Border Patrol and ICE for releasing families in Arizona with little advance warning, saying he had an upcoming call to discuss the issue.

“The first thing we need to do is make sure that our federal government starts to better communicate with our state government, so that we can have a heads-up of what’s happening, how we can be helpful and what we can do,” he said.

State Rep. Tim Dunn, R-Yuma, who represents the area in the Arizona Legislature, followed in Ducey's footsteps.

“Yuma and other border cities simply don’t have the resources to handle an influx of migrants released into the community,” Dunn said in a statement. “It’s unbelievable that Border Patrol is putting both the migrants and the communities in this situation.

"Even worse, this policy is likely to motivate even more migrants to cross the border. The emergency on the border has escalated to a crisis situation that will continue to cause a run on our southern border,” he said.