The Pentagon is still 'mystified' by the presence of drones swarming over key military sites and infrastructure, a senator has revealed. Dozens of mysterious nighttime flights were spotted in northern New Jersey last December, igniting concern amongst civilians and security officials alike. The unmanned aircraft systems - better known as drones - were initially spotted near the Picatinny Arsenal, a military research and manufacturing facility, and over President Donald Trump's golf course in Bedminster. Another swarm of unidentified drones were spotted last November over three US air bases in the UK where American nuclear weapons are stored. Sen. Roger Wicker, chairman of the Armed Services Committee, has now revealed that officials remain perplexed by the sightings, which he suggests could be some type of foreign espionage. 'Clearly, there is a military intelligence aspect of this,' the Republican told 60 Minutes correspondent Bill Whitaker in a December interview that aired this month. Wicker admitted it was 'logical' to believe the drones were 'spying incursions' and although he did not elaborate, the senator revealed other Pentagon officials agree. 'I can tell you, I am privy to, to classified briefings at the highest level,' he said. 'I think the Pentagon and the National Security advisors are still mystified.' An unexplained drone invasion has been seemingly targeting America's worldwide military bases last year, beginning in October with a swarm over Langley Air Force Base in Virginia. Several F-22 jets stationed at Langley had to be relocated to a nearby air base for protection in wake of the drone sightings. The pattern became evident when similar activity was reported over New Jersey's Picatinny Arsenal on November 18. Less than one week later, US bases in England and Germany began grappling with incursions by 'small unmanned aerial systems'. Multiple instances of drones later appeared over New Jersey's Navy weapons station, and Ohio's Wright-Patterson Air Force Base closed its airspace due to similar activity on December 13. Drones were also spotted over a base in Texas on December 18. A former UK security minister last month called for an 'urgent investigation' into the drone activity over the US air bases in England following reports that the sightings have links to Russia. Around 60 British troops were deployed to help the US Air Force in its investigation of the November 2024 incident. Evidence of the movements of three individuals with alleged links to the Kremlin at the time of the sightings suggested Russian state links to the drone activity, a February investigation by the i newspaper revealed. Two of the individuals were believed to have worked as seasonal fruit pickers, according to the report. Former FBI agent and military analyst Ken Gray now warns the threat of foreign nationals using drone technology to spy on the US is growing - and unlikely to stop anytime soon. 'We're going to just see a proliferation of drones everywhere. That includes the possibility of drones being used for nefarious purposes,' he told Fox News yesterday. 'A foreign national operating [a drone] raises a concern about that person being involved in some type of espionage or intelligence gathering.' Citing the use of drones in the Russia-Ukraine war, he warned the devices also 'pose a real risk of being used as a weapon system against targets'. Gray said that even 'hobby-level drones' can be 'modified' to carry dangerous substances or devices, such as explosives. He explained that the government's response to drones is 'not standard' and varies depending on where the aircraft is spotted. The military analyst also warned that identifying the location from which a drone is being operated can prove to be a hard task. Last month, the top general for all air defenses in the US and Canada appeared before Congress to raise alarm about the origin and purpose of swarms of drones that were reported across the country. US Air Force Gen. Gregory M. Guillot, commander of NORTHCOM and NORAD, revealed that there were 350 detections of drones over military installations last year. 'The primary threat I see for them in the way they've been operating is detection, and perhaps surveillance, of sensitive capabilities on our installations,' he warned. Congress, citing concerns about the threats that drones pose to military personnel and defense installations, last month granted a number of federal agencies the authority to take counter measures against credible drone threats. Gray, in his interview with Fox yesterday, noted that any person who operates a drone over a 'restricted space' could face prosecution.