The 114 people were arrested at a school in the Sneinton Dale area
More than 100 people have been arrested in Nottingham over a suspected plan to target a power station.
Police said 114 men and women were arrested in Sneinton Dale on suspicion of conspiracy to commit aggravated trespass and criminal damage.
Officers said they believed those arrested were planning to protest at nearby Ratcliffe-on-Soar power station.
Police said equipment including bolt-cutters was found and they feared a threat to the safety of the site.
A police spokesman said it was thought there was a "serious threat" to the coal-fired power station, which is eight miles south-west of Nottingham.
More than 200 police officers from Nottinghamshire, Derbyshire, Leicestershire, Staffordshire and British Transport Police were involved in the arrests at the Iona School.
There were no reported injuries.
The Ratcliffe-on-Soar power station has previously been targeted by members of the Eastside Climate Action, although the group has denied any involvement in the latest suspected plot.
Eleven people from the group were arrested in April 2007 after chaining themselves to buildings and equipment at the site.
Eon, which operates the power station, said it was helping the police with their investigation.
City councillor David Mellen said the police raided the privately-run school as a result of "an intelligence-led operation".
The operation is understood to have been "intelligence-led"
He said: "I don't know whether it was the school itself being used or the car park.
"Neighbours reported a lot of noise after midnight. It seems to have been used as a rendezvous for people from a wide area."
No-one at the school was available for comment.
Residents in the suburb of Sneinton contacted the BBC with reports of a large police presence in the area.
Tess Rearden, who lives near where the arrests were made, said she saw 20 police vehicles.
She said: "It was all slamming of doors and van doors and all these vans were coming up here - police vans, riot vans.
"My son came out of his bedroom and he said: 'Have you seen what's going on out front?'
"They were all up and down the roads here. It was bedlam, real bedlam."
Residents said handcuffed suspects sang loudly as they were led away.
Susan Lawson, 56, who lives opposite the school, said: "The police said to me 'get in the house and don't come out'.
"Then I saw them bringing people out of the school gates in handcuffs and putting them into vans.
"The vans kept coming back to pick up more of them. Police had big black and yellow bin bags full of something which they took away.
The coal-fired facility is eight miles from Nottingham
"I was shocked, I couldn't get back to sleep afterwards. It was terrible."
Speaking on behalf of Eastside Climate Action, Bob Andrews said: "We don't know anything about the arrests last night.
"It wasn't us and we don't know who has been arrested.
"But if people were planning to shut [the plant] down like we tried to do two years ago then that is great news.
"We would fully support people taking safe and responsible action to stop carbon emissions.
"Ratcliffe is the third biggest single source of CO2 in the country; it has got to be closed down if we are serious about climate change."