(U.S. Senate)-Senator Jon Tester is pushing to eliminate the communication "dead zones" that exist along the northern border.

In a Senate Homeland Security Committee hearing today, Tester urged Homeland Security Secretary Jeh Johnson to fix the communication gaps that limit the ability of Border Patrol agents to communicate among themselves and with local law enforcement while patrolling the northern border.

"I have been told by the folks who work on the ground that there are gaps in communication along the northern border. Are you aware of those gaps in communication and do they exist?" Tester asked.

"It is something that I have heard about, and I know you have an interest in this, and I would not be surprised if there were gaps in communications that should not exist," Secretary Johnson replied.

Federal law enforcement and, state and local first responders have previously raised concerns with Tester that the existing communication gaps create vulnerabilities for both the law enforcement officers patrolling the northern border and regional first responders.

"If we have dead zones on the northern border, this is a concern that is very basic and we need to get answers," Tester added.

Additionally, during the hearing Tester followed up with Secretary Johnson on the concerns he raised earlier this month regarding a new policy that will allow Mexican nationals to more easily enter Canada.

In his letter, Tester outlined a series of steps DHS should take in response to this new policy including identifying additional resources that will be needed to patrol remote areas of the northern border in Montana, pinpointing additional national security threats that will arise from an increase of travelers from Mexico, and tracking and enforcing security plans for Mexican travelers who overstay the six-months they are permitted to visit Canada.

Last year, Tester brought Secretary Johnson's top deputy to Montana to see the challenges facing northern Border Patrol agents firsthand.