What's this story alluding to?

Fox News report that:

"STOCKHOLM, Sweden — Swedish police arrested two maintenance workers on suspicion of sabotage after they tried to enter a nuclear plant Wednesday with traces of the explosive used in the London terror bombings in 2005, officials said.

Police experts with bomb-sniffing dogs were dispatched to search the Oskarshamn nuclear power plant and examine the substance, believed to be triacetone triperoxide, or TATP, which can be extremely dangerous even in tiny amounts.

"It's not something you use at home," Anders Osterberg, a spokesman for plant operator OKG, told The Associated Press. "We're not dealing with toys here."

The two men were contractors hired to perform maintenance work on one of the plant's three reactors, which was shut down on May 11 for an annual checkup, plant spokesman Roger Bergman said. One of them was initially described as a welder, but plant officials later said his occupation was not clear.

Police did not release their identities, but said one was born in 1955 and the other in 1962. The older suspect was "known to police" from prior investigations, police spokesman Sven-Erik Karlsson told AP. He declined to give details.

The men were brought in for questioning after they arrived for work early Wednesday at the power plant, located about 150 miles (250 kilometers) south of Stockholm. The men were stopped because one of them was carrying a plastic bag that was found to contain traces of TATP in a security check, police said.

Bergman said the second man was arrested because "there is some uncertainty about who owns the bag.""

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