“After completing the interrogations with the detained, the prosecutor has today decided to release them, but the suspicions remain,” Sven-Erik Karlsson of the Kalmar police told reporters in Oskarshamn, where the plant is located.
The two Swedes were arrested on Wednesday after a routine security control at the entrance to the plant detected traces of highly explosive material on the handle of a plastic bag one of the men was carrying.
The men, who according to police were born in 1955 and 1964, had been working for several weeks as welders on one of the plant’s three reactors, which had been shut down for maintenance.
A search of that reactor, called reactor two, turned up no explosives or other suspicious material, police said, adding that a second reactor was also being shut down to be searched.
“Both deny any wrongdoing. They have no explanation whatsoever for what has happened,” Karlsson said, adding that one of the men had a criminal record, but only for petty crimes.
The explosive material detected was believed to be TATP, which is relatively easy to make and has surfaced in a number of recent terrorism investigations, including bombings in the Middle East and the London bombings in July 2005.
The men’s homes in the town of Norrköping, some 180 kilometres north of Oskarshamn, as well as their temporary lodgings near the nuclear plant had been searched, but nothing linked to the suspected sabotage plans had been discovered, Karlsson said.
The plastic bag that set off the alarm only contained toiletries, police said, adding that both the bag and its contents had been sent to a national forensics lab for analysis.
The company that runs the plant, OKG, meanwhile tried to defuse speculation that its explosive detection equipment made a mistake.
“When the welder was stopped because the equipment indicated something on his plastic bag, further tests were done,” OKG spokesman Anders Österberg said in a statement, adding “there was no doubt” there was an illegal substance on the bag.
While the two other reactors at the plant remained up and running all day Wednesday, OKG said Thursday morning it was shutting down the one closest to the reactor the men worked on, so it too could be searched.
“When you have access to unit number two you also have some formal access to some areas of unit number one,” OKG spokesman Roger Bergman told AFP.
“Even though we haven’t detected any movement from these two people inside this unit number one we still want to make sure that they haven’t been there,” he added.
Bergman said the shutdown was expected to cost around 5 million kronor ($850,000) a day.
“We don’t know yet how long the reactor will be stopped. It depends on the police investigation,” he said, adding that the third reactor would remain up and running.
The three boiling water reactors at the Oskarshamn plant, which is majority held by German energy giant EON, have been in service since 1972, 1974, and 1985 and produce about 10 percent of Sweden’s electricity.
Nuclear power accounts for nearly half of all electricity production in Sweden, which has 10 working nuclear reactors.