Two nuclear-power plants majority-owned by Vattenfall AB, a state-owned Swedish power company, were targeted by Greenpeace activists, about 70 of whom broke into restricted areas.
The activists targeted the Ringhals plant on Sweden's west coast and the Forsmark facility on the east coast. Combined they produce about 36% of energy consumed in Sweden.
At Forsmark, police initially arrested 43 activists who had scaled the surrounding fence using ladders. At Ringhals, another 16 were arrested after cutting holes through the fence, Vattenfall said.
Vattenfall said in a statement that the activists reached an area with a lower-safety classification and that "security worked exactly as intended."
But as the police, hours later, made a more-thorough search of the Forsmark plant, a couple more activists were found hiding in the so-called operating area, right next to the nuclear reactors.
"As police searched the area two or three more activists were found hiding in a container in the area where the nuclear reactors are located," said Claes Inge Andersson, spokesperson at the Forsmark plant, who maintained that security at the plant had worked as intended.
"The hiding activists were found when the police searched the area, so security has worked as intended as far as we can judge, but we will of course conduct a thorough review of today's events," he said.
Another two activists were also found hiding at the Ringhals power plant hours after the initial arrests.
"The security level is unacceptably low and that it is far too easy to enter the nuclear power plants," said Annika Jacobsson, head of Greenpeace Sweden, a nongovernmental environment organization.
Ms. Jacobsson said the safety deficiencies can be added to those that were presented by the European Commission in a report last week, and she demanded that the Swedish minister of the environment, Lena Ek, who is ultimately responsible for the plants' security, shut down the reactors immediately.
The minister was, according to her spokesperson Erik Bratthall, unimpressed by the security at the two nuclear-power plants in question and annoyed over the fact that there is a continuing discussion about the safety at Swedish nuclear-power plants. She said the safety at the plants is the responsibility of the companies that operate them and she has therefore invited representatives of both Vattenfall and minority-owner E.ON to discuss the matter at a meeting Wednesday.
A European Commission report, which will be discussed by heads of government at a European Union summit on Oct. 18-19, highlighted that if electrical power is lost at Forsmark or the Olkiluoto nuclear plant in Finland, operators would have less than an hour to restore safety functions.
The Forsmark plant responded to the commission's criticism in a statement saying safety measures at the plant have been reviewed in separate assessments by the International Atomic Energy Agency and the business organization WANO.
"Both those assessments show that the facilities are robust and that the nuclear power plant overall has a good international safety standard," Forsmark said.