Story highlights The number of undocumented children has spiked, straining Texas centers

Homeland Security has transferred nearly 1,000 youngsters to Arizona facilities

Better weather, worsening economies in Central America may be factors

Arizona Gov. Jan Brewer objects to earlier family group transfers to her state

More than 100 undocumented children without families were expected to arrive in Arizona from south Texas on Sunday as part of a federal transport of underage immigrants to the state by the Department of Homeland Security, a spokesman said.

Last week, nearly 1,000 "unaccompanied alien children" had already arrived in Tucson and Phoenix from places like McAllen and El Paso, Texas, as part of a resettlement process of the minors, most of whom come from Central America, to their native countries.

Unlike a Mexican immigrant who arrives to the United States, a Central American immigrant cannot be processed as quickly because of proximity to their native country. Homeland Security is prohibited from immediately deporting the children if they are not from Canada or Mexico, causing the backlog of immigrants in U.S. detention centers.

Facilities in Texas were at or near capacity for the immigrants because of a "record increase in underage migrants," which led to the transfer of hundreds to Arizona, a spokesman said.

Although children crossing the border alone has long been an issue, the recent spike could be attributed to better weather or worsening economic conditions in their home countries, officials said. Others simply want to be reunited with their parents, who may have left them with relatives in their native countries.

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Separate from unaccompanied children being sent to the state, family groups were also being sent by the federal government to Arizona, a process that has outraged Arizona lawmakers, including Gov. Jan Brewer. She released a statement Friday saying that DHS was transporting "thousands of illegal aliens and releasing them at bus stations in Tucson and Phoenix."

"I am disturbed and outraged that President Obama's administration continues to implement this dangerous and inhumane policy, meanwhile neglecting to answer crucial questions our citizens demand and deserve," Brewer wrote.

"Not only does the federal government have no plan to stop this disgraceful policy, it also has no plan to deal with the endless waves of illegal aliens once they are released here," Brewer added.

As of late last week, Immigration and Customs Enforcement was no longer releasing "large family groups" at the bus stops in Arizona, a DHS spokesman said, but children under age 17 are continuing to be transferred to the state.

"The situation with the kids are they came by themselves, they have no relatives here, and the consulates can't keep up. They're in limbo. There's no one (back home) to deport them to," a DHS spokesman told CNN.

Raising a larger humanitarian concern are the conditions to which the immigrant children are arriving.

A facility in Nogales, Arizona, with capacity for about 1,500, does not have enough food or beds to accommodate the current demand, a spokesman said.

There are currently no showers for the immigrants, either, but those were expected to be in place by Tuesday, according to a spokesman.

"The Nogales processing center is equipped and used for processing apprehended individuals. The Tucson Sector has secured additional services such as a Health and Human Services medical screening area, additional bedding, shower areas and laundry facilities. Vendors have been contracted to provide nutritional meals, FEMA will be providing counseling services and recreational activities," U.S. Customs and Border Protection said in a statement.

"Upon completion of CBP processing...custody determinations will be made on a case-by-case basis," the statement said.

The record spike in migrants coming from Central America and crossing into the United States via Mexico is not expected to slow down, a spokesman told CNN.

More than 60,000 unaccompanied juveniles are expected to cross in 2014, said Chris Cabrera, vice president of the National Border Patrol Council in the Rio Grande Valley, a U.S. Border Patrol workers union.

"We are seeing numbers that we've never seen before in this part of the country," Cabrera told CNN last month. "Yesterday, we had 60 minors in one station alone. You're talking kids from 17 years old, on down to some that are 5 or 6 years old, traveling by themselves."

Last year, roughly 10% of people caught by Border Patrol agents were minors, according to a Border Patrol official.