Swedish police said that the two workers from a nuclear power station, who were detained Wednesday because officials found traces of a highly explosive substance on them, have been released Thursday. Their identities were not made public.

Plant officials said that security guards found traces of TATP on the handle of a plastic bag that one of the workers was carrying. They were arrested immediately.

According to Reuters, triacetone triperoxide is an extremely unstable explosive when it is subjected to heat, friction and shock. The explosive was used in the 2005 London transit bombings.

Kalmar County Police official Kenth Andersson confirmed that the two men were released Thursday at 12.15. Police are expected to hold a conference later this day.

Just to be sure, officials from the Oskarshamn plant shut down one of its reactors.

Reactor O1 was shut down Wednesday because there was the possibility that the two maintenance workers could have plotted to sabotage the plant, as they had access to some areas near the reactor.

The plant had only one reactor in function, given the fact that reactor O2 was shut down on May 11 for an annual verification.

According to The Associated Press, plant spokesman Anders Osterberg said that the shutdown of one reactor will cost the plant to lose about $840,000 a day, but he also said that safety is more important than money.

The Oskarshamn nuclear plant is owned by Germany's E.ON and Finland's Fortum.