A police cordon remains in place as investigations into unidentified chemicals continue.
Officers from Suffolk Police carried out a pre-planned warrant on a property on Normanshurst Close, in Lowestoft, on Sunday afternoon.
After military grenades, a firearm and unidentifiable chemicals were discovered during a search of the property, a 100m cordon was established with 60 homes evacuated, including on Fir Lane.
A 59-year-old Suffolk man was arrested at the scene on suspicion of possessing a firearm.
He has now been further arrested on suspicion of being concerned in the commission, preparation and instigation of acts of terrorism, a spokesperson for the Met Police confirmed.
He has been detained and remains in police custody in Suffolk.
Usually, police are required to charge or release suspects within 24 hours, although people suspected of terrorism can be detained for 14 days without charge.
Former Eastern EDL regional organiser turned counter-extremism campaigner Ivan Humble, from Lowestoft, said: "While there is an ongoing investigation, it is essential that the authorities are left to do their important work.
"At this stage, rather than speculate or spread rumours, we should focus our efforts on reassuring all of the residents and neighbours of Lowestoft to continue being the steadfast and resilient community it has always been."
Emergency services have remained on the scene throughout, with the cordon since being reduced to the searched property and three neighbouring homes.
Following the search, detective chief superintendent Alexis Boon, of the Met Police Counter Terrorism Command, said there was nothing to suggest an ongoing threat to the public.
As well as Army Explosive Ordnance Disposal officers and Suffolk Fire and Rescue crews, charity volunteers were called to the scene, with 15 Salvation Army volunteers on-hand to serve refreshments to the emergency workers.
The call out marked the 400th incident the volunteer team responded to since being founded in 1978.
Michael Baker, coordinator of The Salvation Army's Suffolk Emergency Response Team, said: "For more than 40 years, Salvation Army volunteers have been privileged to support the emergency services and first responders at major incidents across Suffolk. As a Christian church and charity, we seek to alleviate distress wherever it is found, offering refreshments and pastoral support as required."
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