Hundreds of undocumented immigrants have been dropped off in Arizona at bus stations after being flown from Texas, officials announced.

Andy Adame, a spokesman for the Border Patrol in Tucson confirmed that about 400 immigrants apprehended in the Rio Grande Valley of Texas were flown to Arizona to be processed. Adame said that the Border Patrol in south Texas doesn't have enough manpower to handle the recent surge in undocumented immigrants in south Texas. 

Border enforcers are concerned that these undocumented immigrants could get lost in the mix and end up staying in the U.S. They fear that this would encourage even more immigrants to come into the U.S. illegally.

"This is a huge concern," said Ira Mehlman, a spokesman for the Federation for American Immigration Reform, a Washington, D.C.-based group that advocates for more immigration and border enforcement.

"This is exactly the incentive for people to cross the border illegally," he said.

Immigrant supporters argue that dropping off immigrants at bus stations without food, water or directions is inhumane and unsafe.

"It's not safe healthwise, and we are concerned for their physical safety," said Cyndi Whitmore, a volunteer with the Phoenix Restoration Project, an advocacy group that has been going to the bus terminal in Phoenix to help. 

Laurie Melrood, a volunteer family advocate in Tucson, has noticed more women and children being dropped off at bus stations. 

"The conditions under which they are released are inadequate and inhumane," she said. 

Volunteers in Phoenix and Tucson are helping immigrants at bus stations with food, water and other necessities.

Illegal immigration in the Tucson Sector has fallen greatly in recent years but has skyrocketed in the Rio Grande Valley. South Texas is becoming the gateway for immigrants to enter the U.S.

When immigrants, usually families, are apprehended trying to cross the border illegally, they are screened, released under supervision and required to report with immigration officials in their area within 15 days.

U.S. Immigration and Customs Enforcement focus on the immigrants that are deemed as criminals; the others are often forgotten.

ICE was unable to confirm whether the 400 undocumented immigrants in Arizona were released.