Police sniffer dogs were removed from Reactor 2 shortly before midnight on Wednesday.
“They didn’t find anything,” Anders Österberg, a spokesman for OKG, the company that runs the plant, told news agency TT.
Police plan to send the sniffer dogs into Reactor 1 on Thursday afternoon.
“If they don’t find any traces of explosives there either we will consult with police about reaching a decision to start up the reactor,” said Österberg.
Oskarshamn is the only nuclear palnt in Sweden that does not have the necessary equipment in place to check everybody entering the plant for explosive materials. The two men found on Wednesday to be carrying the explosive TATP were detected during a random check.
New rules were introduced on January 1st this year requiring all nuclear plants to check everybody entering the grounds. But OKG did not acquire the requisite equipment and instead requested an extension until 2010.
The Swedish Nuclear Power Inspectorate turned down the request and threatenen OKG with a fine of one million kronor if it fails to have the equipment in place by December 15th.
Both men arrested on Wednesday were contractors who had been working at the Oskarshamn nuclear plant in southern Sweden “for some time,” but police said the link between the two remained unclear.
One of the men was arrested and questioned early after routine tests at the entrance to the plant detected traces of highly explosive material on the handle of a plastic bag he was carrying.
Police said that the men were born in 1955 and 1962 and that one of them had a criminal record, but did not disclose their identities.
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.
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.
Österberg said OKG had received no threats against the reactors, and terrorism expert Lars Nicander told TT there were no known threats against the plant and no reason to suspect an organised group was behind the suspected sabotage attempt.
Nuclear power accounts for nearly half of all electricity production in Sweden, which has 10 working nuclear reactors.