FIRST ON FOX: Sen. Chuck Grassley, R-Iowa., is seeking information from top border and homeland security agencies about the potential threat posed by drones operated by terrorist groups and cartels at the southern border amid heightened awareness of a terror threat in recent weeks. 

Grassley sent letters to Customs and Border Protection (CBP), Immigration and Customs Enforcement’s (ICE) Homeland Security Investigations (HSI) and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) citing reports that Mexican cartels have increased their use of the drones at both sides of the U.S.-Mexico border.

"These drones are used by the cartels to carry out targeted assassinations and violent attacks by dropping explosives in Mexico, monitor and gain reconnaissance on the movements of U.S. Border Patrol agents and other U.S. law enforcement officers, and track the progress of their smugglers illegally crossing into the U.S.," he said. 

MAYORKAS CONFIRMS OVER 600,000 ILLEGAL IMMIGRANTS EVADED LAW ENFORCEMENT AT SOUTHERN BORDER LAST FISCAL YEAR

Sen. Chuck Grassley speaks into mircrophone during hearing

Senator Chuck Grassley, R-Iowa, wrote to Customs and Border Protection, Immigration and Customs Enforcement’s Homeland Security Investigations and the Bureau of Alcohol, Tobacco, Firearms and Explosives. (Al Drago/Bloomberg via Getty Images)

Department of Homeland Security has noted the use of drones by cartels as a threat to the U.S. in its FY 24 threat assessment. The assessment said that Mexican cartels are using drones "to enhance and protect their operations." 

"In 2022 and 2023, US officials observed human smugglers using commercially available UAS [unmanned aerial surveillance] to monitor migrants and law enforcement across the border. Drug traffickers also use small commercial UAS to augment drug smuggling and to surveil US and Mexican law enforcement activities, helping them avoid some interdiction operations," it said. 

BORDER PATROL STOPS RECORD NUMBER OF PEOPLE ON TERROR WATCH LIST AT SOUTHERN BORDER

On Tuesday, DHS Secretary Alejandro Mayorkas told lawmakers that its counter-drone authority will expire on Nov. 18, hurting CBP's ability to patrol the southwest border and "intercept cartel drones ferrying drugs and other contraband through the air." 

CBP, meanwhile, says it is surging resources, including technology and personnel to the border, along with greater regional cooperation with countries like Mexico. Officials have highlighted the installation of "strategically placed advanced technology" like linear ground detection systems and automated surveillance towers – along with CBP drones, aerostat radar systems and other forms of surveillance. Officials say that allows agents to surveil, detect and stop individuals, drones, weapons and other contraband entering the U.S. 

Grassley also cited media reports of a raid in Mexico last month that revealed a workshop for drone-carried explosives. The Associated Press reported that state police found 40 small cylindrical bombs with fins meant to be released from drones, as well as bomb-making materials.

HIGH MIGRANT NUMBERS BREAK MULTIPLE RECORDS IN NEW BLOW TO BIDEN BORDER STRATEGY

Grassley connects that threat to the reported use of drones carrying explosives by Hamas terrorists in its terrorist atrocities against Israel, an attack that has renewed concerns about the potential terror threat posed to Americans at the U.S.-Mexico border.

Texas patrol boat by US-Mexico border

Texas Highway Patrol officers monitor the Rio Grande at the U.S.-Mexico border in Eagle Pass, Texas, on Friday, Oct. 6, 2023. (Alejandro Cegarra/Bloomberg via Getty Images)

"The horrific attacks by Hamas terrorists against the people of Israel and their use of weaponized drones to deploy explosives further highlight the need to secure the U.S. border from these types of national security threats," he said.

Republicans have pointed to the number of terror watch list encounters at the southern border, the increased numbers of "gotaways" in FY 23, and warnings by CBP that fighters from Hamas and Hezbollah could attempt to enter the U.S. by the southern border as signs of an increased threat.

"The recent heinous attacks by Hamas terrorists, who used arms and explosive-rigged drones against Israeli civilians, underscores the very real risk that could happen at our southern border and against Americans," he warned.

CLICK TO GET THE FOX NEWS APP

In his letters, Grassley called for a slew of information from the departments including the number of drones that crossed into U.S. territory, ties to cartels or terror groups of operators, the types of drones used and the types of payload.

He also wants to know whether terrorist groups or those tied to such groups have advised cartels on how to make bomb-carrying drones, and what the agencies are doing to combat the threat, including assistance the agencies have offered to Mexico.

The ATF told Fox News Digital it has received the senator’s letter and looks forward to responding to him, while ICE also responds to congressional correspondence through official channels. CBP confirmed it has received the letter and also responds directly to congressional correspondence. 

The Associated Press contributed to this report.