Detectives have been granted extra time to question two 14-year-old boys arrested over the weekend on suspicion of plotting a terrorist act in the north of England.

The teenagers, who live two miles apart in the market town of Northallerton in North Yorkshire, can now be held until Wednesday following their arrest on Saturday.

Three residential addresses, including the boys’ homes, were raided over the weekend and the boys were detained on suspicion of hatching a terror plot. Police have said they believe it was an isolated incident and that the wider community is not at risk.

A school in the town has become the focus of the investigation, according to parents of pupils, who have claimed there were fears for the safety of staff and children.

A spokesman for North Yorkshire county council said: “The school is supporting the police in their investigation. Police continue to investigate with an open mind to establish what, if any, offences have been committed.

“The school understands that parents and carers may have concerns as a result of these arrests. We would like to reassure them that the safety of the school is paramount and we are working with the police to support our students and prioritise their safety at all times.”

The teenagers are being interviewed in West Yorkshire on “suspicion of preparing for an act of terrorism” under section 5 of the Terrorism Act 2006 after intense police activity in Northallerton, which is known as the county town of North Yorkshire.

Police going door-to-door on Saturday also told residents that they were examining Google Street View grabs on computers seized during their searches.

One of the boys lives with his father and younger brother in a smart, well-kept home off an affluent tree-lined street.

A neighbour said: “There were about 10 police cars, including unmarked cars, here on Saturday from 8am until after midnight. It was a very big operation and they appeared to be searching the house, the garage, the garden and a Peugeot car. There have been some problems with the kids yelling abuse and causing problems and noise in the street. There has been some abusive language.”

There had also been concern from neighbours that the boys in the household were arriving home unaccompanied by taxi from school.

The second property to be searched was in a village just outside Northallerton. A neighbour said: “There were four police cars and a van parked here all weekend, they seemed to be searching a house. The family have a son who is around 14 and he has been in some bother at school recently.

“It was a big police operation and it went on for quite a while so we knew it had to be something serious but this is the last place you’d expect anything to do with terrorism.”

The police investigation centred on a disused garage building with a blue metal shutter door in the town’s Romanby area. A neighbour said: “There is a hole in the fence behind the building, which local kids climbed through and got inside the building.

“There had been a little bit of trouble – some drugs paraphernalia was found – but nothing on the scale of what has been happening this weekend. We knew it had to be something significant because of the scale of the police operation. They were searching the building and the area around it but we weren’t told what for.”

The investigation is being led by the north-east counter-terrorism unit, with assistance from the North Yorkshire police force.

A spokesman said: “Officers from counter-terrorism policing north-east have this morning [Monday] been granted a warrant of further detention for two 14 year olds from Northallerton, who were arrested on suspicion of terrorism offences on Saturday.

“Their detention is now authorised until Wednesday 2 November 2017 and the boys remain in West Yorkshire for questioning. Both boys were arrested as part of an ongoing police-led investigation on Saturday 28 October, on suspicion of preparing for an act of terrorism, contrary to section 5 of the Terrorism Act 2006.

“Since the weekend, searches have taken place at a number of locations in the Northallerton area. These include searches at three residential properties, which have now concluded.”

A North Yorkshire police spokesperson said: “Officers believe that this is an isolated incident and the wider community are not at risk. We appreciate the cooperation of local residents while the investigation continues.”

People are urged not to comment or speculate on social media as this may prejudice any potential criminal proceedings.