Nearly one-third of the cameras in the Border Patrol’s primary surveillance system along the southern U.S. border are not working, according to an internal agency memo sent in early October, depriving border agents of a crucial tool in combating illegal migrant crossings.

“The nationwide issue is having significant impacts on [Border Patrol] operations,” reads a Border Patrol memo sent to a sector of agents along the southern border and obtained by NBC News

The large-scale outage affects roughly 150 of the 500 cameras perched on surveillance towers along the U.S.-Mexico border. It was due to “several technical problems,” according to the memo. The officials, who spoke on the condition of anonymity to discuss a sensitive issue, blamed outdated equipment and outstanding repair issues.

The camera systems, known as Remote Video Surveillance Systems, have been used since 2011 to “survey large areas without having to commit hundreds of agents in vehicles to perform the same function.” But according to the internal memo, 30% were inoperable. It is not clear when the cameras stopped working.

Two Customs and Border Protections officials said that some repairs have been made this month but that there are still over 150 outstanding requests for camera repairs. The officials said there are some areas that are not visible to Border Patrol because of broken cameras.

A Customs and Border Protection spokesperson said the agency has installed roughly 300 new towers that use more advanced technology.

“CBP continues to install newer, more advanced technology that embrace artificial intelligence and machine learning to replace outdated systems, reducing the need to have agents working non-interdiction functions,” the spokesperson said.

The Border Patrol union in Laredo, Texas noted the issue last week on Facebook. It told its members that it “shares your concerns that inoperable camera towers along the border are causing serious officer safety and border security concerns.”

“We hope this issue is resolved soon as the problem has been ongoing for quite some time!” the union added in the post, dated Friday. “The American taxpayer has made significant investments in technology along the border, and they expect that this technology is operational.”

The internal Border Patrol memo obtained by NBC News blames a different federal agency for the problem — the Federal Aviation Administration. The FAA, which services the systems and repairs the cameras, has had internal problems meeting the needs of the Border Patrol, the memo says, without elaborating on what those problems are.

The FAA will send personnel to the southern border to work on the cameras, the memo says.

Border Patrol leaders are considering replacing the FAA with a contractor that can provide “adequate technical support for the cameras,” it adds.

A third Customs and Border Patrol official said the agency is trying to fix a significant problem that has not been properly managed for the last 20 years.

An FAA spokesperson declined to comment.

The Department of Homeland Security’s budget request to Congress, via the White House, has routinely asked for more money to restore surveillance systems along the border.

House Republicans blocked a bipartisan bill this year that would have significantly improved surveillance systems, hired additional Border Patrol agents and resumed border wall construction.