STOCKHOLM : Two Swedish contractors were arrested on Wednesday suspected of preparing to sabotage a nuclear power plant in southern Sweden, after traces of explosives were found on one of the men, police said.

"Two Swedish men were arrested ... The prosecutor suspects them of sabotage," Sven-Erik Karlsson of the Kalmar county police told AFP, adding that both men were contractors who had been working at the Oskarshamn nuclear plant "for some time."

One of the men was arrested and questioned early Wednesday after routine tests at the entrance to the plant detected traces of highly explosive material on the handle of his plastic bag.

Karlsson said the link between the two, whose identities were not disclosed, remained unclear, but said they had been contracted for maintenance work on one of the reactors.

A spokesman for the OKG company that runs the plant, Anders Oesterberg, told AFP that the two were welders and that one of them had been working inside the plant for two weeks.

He said sniffer dogs would be sent in to search the area around the shut down reactor they had been working on.

"One must of course take into account the information we have about where these people have been working ... and in cooperation with the police and bomb sniffing dogs search these areas to make sure these people have not left behind any explosives," Oesterberg said.

"It is a security measure," he said, adding that around 100 people had been evacuated from the area where the explosive traces were detected.

The plant's two other reactors were running as normal on Wednesday, he said.

The explosive material 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.

It was the same type of explosive that Al-Qaeda "shoe bomber" Richard Reid tried to detonate on a Miami-bound flight in December 2001, three months after the September 11 attacks in New York and Washington that killed some 3,000.

Although the recipe for TATP is complex, its ingredients can be found in simple household goods: sulphuric acid - found in drain cleaner - hydrogen peroxide, and acetone, often a constituent of nail polish remover.

The Oskarshamn plant, which is owned by German energy giant EON, has three boiling water reactors, in service since 1972, 1974, and 1985.

The three reactors produce about 10 percent of Sweden's electricity, according to the plant.

"Our joint assessment is that the security of the reactors was never threatened," OKG's Thuring said.

"We are however taking all necessary measures to verify this, of course" he added.

Nuclear power accounts for nearly half of all electricity production in Sweden, which has 10 working nuclear reactors. - AFP/ms