Campaigners protesting at Britain's biggest coal-fired power station are being stopped and searched by police as they enter and leave the campsite.
Police have found no evidence to link the damage to the protest
The move comes after police issued a warning to campaigners when power lines were cut down at Fryston, near Castleford, West Yorkshire, on Tuesday.
About 500 people have camped near Drax in Selby, North Yorkshire, to protest over carbon dioxide emissions.
Police found no evidence of a link between the damage and the protest.
But campaigners were warned not to break the law.
A spokeswoman for event organisers, Camp for Climate Action, said she could not comment on the damage.
But, she said, campaigners objected to being searched by police.
She said: "We think it is unreasonable. People have come here to talk about climate change, and to educate themselves with workshops.
"Some people are choosing not to leave the site as a result of this."
Campaigners have also been protesting outside Hartlepool nuclear power station. Six people who chained themselves to the power station's gates were arrested on Tuesday.
'Firm and swift'
North Yorkshire Police Deputy Chief Constable Ian McPherson said: "It's certainly a coincidence that there should be three events within 24 hours all involving the power supply.
"I would be very disappointed if it turned out that the demonstrators at the climate camp were involved in any illegal action."
Mr McPherson said while the force would facilitate a lawful and peaceful protest it would deal "firmly and swiftly" with anyone who broke the law.
Police have been drafted in from across Yorkshire in case there is any trouble.
A large camp has sprung up close to the Drax power station
The protesters, who are camping on land next to Barlow Common nature reserve, are planning a day of "mass action" on Thursday in an attempt to shut down the site.
The power station has secured an injunction prohibiting any trespassing on the site and restricting the use of a nearby footpath.
Drax said it wanted to ensure the protesters did not force the station to close or put their own safety at risk.
It had no objection to "peaceful and lawful demonstration" but did not want protesters exposed to the dangers and hazards "inherent to our highly complex industrial site".