Threat levels have been increased in Sweden after explosive material was found on a truck near a nuclear power plant. According to authorities, there was no detonator attached to the explosive material found under a truck during a routine security check, and it could not have caused much damage. Police say that they are looking into the case as a possible sabotage attempt, authorities said Thursday. The nuclear power plant at Ringhals, which houses four reactors, is the largest in Sweden. Police said that they do not suspect of the driver of the truck of involvement.