U.S. troops will remain on the Southern border through fall, Defense Department officials told the House Armed Services Committee.

Through Sept. 30, military personnel will support mobile surveillance cameras in Arizona, California, New Mexico and Texas. Through March 31, troops will also roll out about 150 miles of concertina wire on existing barriers, defense officials said. That would be in addition to the 70 miles of concertina wire already laid by troops.

There are about 2,300 active-duty troops, mostly soldiers, on border duty today, and several thousand more could be deployed, defense officials said.

“The military’s presence and support increase the effectiveness of CBP’s border security operations, free U.S. Border Patrol agents to conduct law enforcement duties at the southern border and enhance situational awareness to stem the tide of illegal immigration, human smuggling, and drug trafficking along the southern border,” defense officials said in a statement. CBP is the acronym for Customs and Border Patrol, a division of the Department of Homeland Security.

Soldiers have been providing aviation and engineering support, building temporary barriers and placing concertina wire since October. The cost so far has been about $240 million.

“The Department of Defense has a long history of supporting border security,” said John Rood, undersecretary of defense for policy. “DoD has supported efforts to secure U.S. borders since the early 1990s.”