Counter-terrorism officers have arrested five men near the Sellafield nuclear plant in northwest England.
The men are all Bangladeshi, aged in their 20s, from London.
The ABC reports they were detained after a routine vehicle check and are being held under the Terrorism Act.
Initial reports suggest the men were filming the area.
Sellafield includes a number of nuclear fuel reprocessing facilities and waste treatment plants.
The site has been in operation since the 1940s.