NOGALES — Three dark-colored helicopters thundered through the skies over the Border Patrol station minutes before National Guard troops filed out the building’s front doors Friday afternoon.

The troops stood in a half-dozen rows alongside Border Patrol agents as Gov. Doug Ducey said there was “no militarization of the border” and praised the Trump administration for “finally taking action” to secure the border.

The Arizona National Guard troops will support Border Patrol agents charged with law enforcement on the border, Ducey said at a news conference.

Ducey plans to send 338 Arizona National Guard troops to help with border security, including 60 who arrived in Nogales this week and 110 who will provide air support from a base in Marana, the Associated press reported.

National Guard troops previously were deployed to the U.S.-Mexico border in 2006 and 2010.

Rodolfo Karisch, chief patrol agent for the patrol’s Tucson Sector, told reporters that immigration enforcement remained the responsibility of Customs and Border Protection and other agencies within the Department of Homeland Security.

CBP in Arizona has a “long and lasting relationship” with the National Guard, Karisch said. The troops will help agents with aerial support, road maintenance projects and by operating camera systems.

With that help, agents will “get back into doing law enforcement work,” Karisch said.

Karisch said the agencies were developing a “planned, phased approach” for using the National Guard troops on the border. The initial deployment will be between ports of entry, but at a later date they likely will be used to support customs officers at ports of entry.

When asked whether deploying troops to border areas would exacerbate the perception of Southern Arizona as a dangerous area and hurt local economies, Ducey said as governor he had to balance the economy with public safety and “public safety has to come first.”

Troops are already stationed at the Texas-Mexico border. The California governor recently announced he would send troops to that state’s border with Mexico.

The federal government is funding the deployment, but the troops will be under the control of the states’ governors. This arrangement, known as Title 32 duty status, is an exception to a federal law that prohibits the use of the military in law enforcement.

The National Guard troops “will not perform law enforcement activities or interact with migrants or other individuals detained by DHS without approval from (Defense Secretary James N.) Mattis,” according to a Department of Defense news release about the deployment.

The troops will not be armed unless they are in circumstances that might require self-defense.

Throughout Friday’s news conference, Ducey cited a recent “surge” in border apprehensions — a proxy widely used to estimate total illegal crossings — as the reason for the deployment of the Arizona National Guard to the border.

Border Patrol agents in the Tucson Sector made nearly 5,800 apprehensions in March, compared with 2,150 in March 2017, CBP records show. Along the entire U.S.-Mexico border, agents made nearly 37,400 apprehensions in March, up from 12,200 in March 2017.

The recent spike in apprehensions followed historic lows in the first year of the Trump presidency.

Contact reporter Curt Prendergast at 573-4224 or cprendergast@tucson.com or on Twitter @CurtTucsonStar