Nearby residents have been told there is no cause to fear for their safety
A 19-year-old man has been arrested in Bristol under the Terrorism Act, police have said.
The man, from the Easton area, is being held as part of investigations into Andrew Ibrahim, 19, who was charged under the Terrorism Act in April.
Officers from Avon and Somerset Police are conducting a forensic search of the man's address. A second nearby property is also being searched.
Police have been scrutinising CCTV footage since Mr Ibrahim's arrest.
They have been "painstakingly" working their way through thousands of days worth of images and looking at more than 2,000 exhibits and more than 2,500 documents, Avon and Somerset Police said.
No armed officers were involved in the latest arrest and there was "no suggestion" of any danger to members of the public, the force added.
Letters have been posted through the doors of neighbouring homes in the Easton area of Bristol on Monday to reassure residents there is no cause to fear for their safety.
Mr Ibrahim, of Westbury-on-Trym, Bristol, has appeared in court accused of plotting to commit acts of terrorism.