The U.S. Border Patrol is on a hiring spree for a very specific type of agent: a female one.

Only 5 percent of its approximately 21,000 agents around the country are women, and the agency has long called this a problem.

It is especially troublesome in the Southwest, where nearly 120,000 women were caught crossing the border illegally in the fiscal year that ended Oct. 31. That's a significant increase from fiscal year 2011, when about 43,000 women were apprehended. The agency's southwest region includes Arizona, Texas and California.

But while the number of women who cross the border has grown, the number of female border agents has remained low.

That's a concern for Juanita Molina, executive director of the Border Action Network, an immigrant rights group in Tucson.

"Most women are victimized by men, so having a first responder who's a man inherently creates mistrust," Molina said.

Six in 10 female migrants are sexually assaulted while crossing the border, according to Amnesty International. Many more become sick or lost while crossing.

The Border Patrol Search, Trauma and Rescue team is responsible for rescuing lost or injured migrants and administering first aid. In Tucson, only one of the agents on this elite team is a woman. Nationwide, four are.

The Border Patrol responds to hundreds of cases each year of immigrants who need to be rescued while crossing the desert. The agency conducted 509 rescues in the 2014 fiscal year in the Tucson sector, although that's a much smaller figure than in past years.

The Rio Grande Valley Sector in Texas has seen the largest number of migrants come through. Almost 49 percent of migrants who are caught crossing in Rio Grande Valley are women.

Last summer, the agency was overwhelmed by a surge in unaccompanied minors and women with children who were crossing via Texas and turning themselves in to the Border Patrol.

Most were from Central America, and many were released with the expectation that they would report back to immigration officials within 15 days. Others were sent to a detention center for women and families in Artesia, New Mexico. Immigration officials keep children only in detention centers that are specifically for families.

U.S. Customs and Border Protection, the Border Patrol's parent agency, acquired a federal exemption to recruit strictly female agents.

Tucson Sector spokeswoman Shevannah Wray says at most federal law enforcement agencies, 15 percent of sworn officers are women.

She says one other reason for the need for female agents is for search purposes. Although the Border Patrol allows male agents to search female migrants, it prefers that women do so, Wray said.

She added the quest for more female agents comes down to one simple thing: "to diversify our workforce and to make it reflect the workforce of the whole United States."