Two 14-year-old boys have been arrested on suspicion of preparing an act of terrorism.
The teenagers were arrested in the North Yorkshire market town of Northallerton on Saturday.
The North East Counter Terrorism Unit said a number of properties were being searched in the area.
North Yorkshire Police said: “Officers believe that this is an isolated incident and the wider community are not at risk.
“We appreciate the cooperation of local residents whilst the investigation continues.”
The teenagers are being questioned at a police station in West Yorkshire.