Residents near a house which was raided by anti-terror police overnight were evacuated from nine properties yesterday "as a precautionary measure".
The nine homes are in the Walton Drive area of High Wycombe.
"This is standard practice in operations of this kind and there is no need for anyone to be alarmed," said Supt Mike Ismay of Thames Valley Police.
"At this time we don't know how long people will have to be evacuated for, but we will do our best to keep disruption to a minimum."
The High Wycombe operation is centred on a three-bedroom semi-detached ex-council house where locals said a family with three sons and two daughters had lived for the past 15 years.
Neighbours said two of the brothers, now married still lived there with their wives, but a third brother no longer lives there.
Former friends said the men used to be well known in the area but had not been seen very much in recent years.
Philip Redfern said: "They are very quiet, they keep themselves to themselves which is very strange because this is a very tight community.
"They were a few years older than me but we were in the same school.
"They used to go out and play football with us in the park when they were about 18 or 19, as time went on and we got a bit older we went our separate ways."
In east London, neighbours of a flat believed to be linked to the terrorist plot said they saw about 20 officers raiding the property on Wednesday night.
Police rammed the front door to a house divided into a number of flats in Forest Road, Walthamstow, shortly before midnight.
John Weir, aged 50, who lives opposite the terraced property, said plain clothed officers in unmarked cars silently lined up opposite the house before the raid.
He said: "At about 10.30pm unmarked police cars all lined up on the street and just sat there. About 11.50pm two vans came up the road and parked at either end of the street. Then about 20 officers, four of them were in uniform, ran up and bashed the door in.
"None of them had weapons on them although they weren't local police. I know that because our local police station is just up the road and it wasn't the officers from there. They did everything very quietly."
Mr Weir said officers headed upstairs to a first floor flat, which they searched by torchlight.
He said: "The only light they turned on were the ones just inside the front door. When they went upstairs they didn't turn any lights on and you could see the torches flashing as they started their search. They were swarming all over the place.
"There must have been forensic officers there because I saw them taking tool boxes and lots of equipment in."
However, Mr Weir said he did not see police take anyone out of the house or remove any property.
Yesterday afternoon, uniformed police officers were still guarding the front and back entrances to the property. Damage to the front door where police had rammed it open could be clearly seen.
Police also raided a second house in nearby Folkestone Road in the early hours of this morning.
A neighbour, who asked not to be named, said: "All we know is that the police came last night and they told us that one young man was arrested."
The neighbour said: "I think there was a man in his 20s living there, maybe with his family, who converted to the Muslim faith a while ago. But I couldn't tell if that was the same person as was arrested."
Specialist Met Police search teams were last night scouring an area of woodland in High Wycombe, half a mile from another residential address in Micklefield Road which was being guarded by police officers.
It is understood this house, a Victorian semi, was also raided over-night by anti-terror squads.
Neighbours said the house had been lived in by an Asian family for around 15 years and that they did not interact much with fellow residents.