Two Latvian nationals legally living in the United Kingdom were arrested under Section 4 of Britain’s National Security Act of 2023 on Thursday after breaching a perimeter fence at RAF Molesworth, a sensitive British military base housing critical U.S. and NATO intelligence operations, Reuters reported.

The arrests triggered a major counterterrorism investigation into the security breach at the strategic installation, which serves as a central intelligence hub supporting American military commanders across Europe and Africa.

The base is also undergoing a $556.5 million expansion centered on the Joint Intelligence Analysis Complex (JIAC), a facility designed to consolidate 20 intelligence facilities and accommodate more than 1,000 personnel, according to reports.

The suspects, ages 32 and 36, were discovered inside the base around 2 a.m. Thursday following an extensive security sweep.

Ministry of Defense Police officers conducting routine patrols first raised the alarm around 10 p.m. Wednesday after finding an abandoned vehicle near the perimeter.

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Bomb disposal specialists cleared the vehicle before armed officers discovered a fence breach and located the men inside.

Initially detained on suspicion of trespass and criminal damage, both men were rearrested under the National Security Act for entering a prohibited place for a purpose prejudicial to the United Kingdom. They remain in custody as counterterrorism detectives execute search warrants at two residential properties in nearby Peterborough.

Managed by the U.S. Air Force’s 423rd Air Base Group, RAF Molesworth is a nonflying installation dedicated to joint intelligence and command operations.

It houses intelligence elements for U.S. European Command, U.S. Africa Command and the NATO Intelligence Fusion Centre.

During World War II, the airfield was used by the U.S. 15th Bombardment Squadron. In 1973, the airfield was officially deactivated before transitioning into its current role as an intelligence center.

Construction on the JIAC broke ground April 12, 2024, with onsite work beginning that spring. The facility is scheduled for completion in summer 2028.

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RAF Molesworth is a nonflying installation dedicated to joint intelligence and command operations. (REUTERS/Chris Radburn)

A 2024 Defense Department release described the base development as part of the department’s overall European Infrastructure Consolidation efforts.

“It will combine 20 facilities and over 1,000 DIA personnel into one location. Among others, it will host members of the NATO Intelligence Fusion Centre, Battlefield Information Collection and Exploitation System, U.S. Africa Command, U.S. European Command and U.S. Air Force elements in a cross-agency, multi-mission collaboration.”

At the time, Defense Intelligence Agency Deputy Director Suzanne White said the facility would enable “the U.S. and allies’ shared mission of ‘outpacing our strategic competitors and addressing threats together wherever they may arise.’”

The Defense Department designed the project with a two-stage procurement strategy, allowing stakeholder agencies to provide feedback and streamline scheduling requirements.

Following the intrusion, U.S. European Command praised the swift British response.

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Two Latvian nationals legally residing in the United Kingdom were arrested under Section 4 of Britain’s National Security Act of 2023 on Thursday after breaching a perimeter fence at RAF Molesworth, a sensitive British military base housing critical U.S. and NATO intelligence operations. (REUTERS/Chris Radburn)

“While we assess the global security posture, U.S. forces remain at the highest state of readiness,” the command said in a statement.

“We would also express our gratitude to the UK for the close partnership with U.S. forces on matters of security.”

British counterterrorism officials cautioned against drawing premature conclusions about possible espionage or terrorist motives.

“We’re very aware of the recent heightened interest and concern around military sites,” Counterterrorism Policing London commander Helen Flanagan said.

Flanagan added that investigators have not established a connection between the Molesworth breach and recent security concerns at RAF Fairford, another British base used by U.S. strategic bombers.

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“We are keeping an open mind at this stage and inquiries are very much ongoing,” she said.

Fox News Digital has reached out to the Pentagon and the CIA for comment.