[botmeister]

I should add that the Tsar Bomba was built in 1961, so perhaps there are bombs much more powerfull that could be built today. However, the physics of nuclear bombs remains static, so I'm not sure that a modernized version could do much better than what was done 40 years ago, unless there's another kind of physics involved.

In any event, one would suspect that had a nuclear bomb been used, a whole lot of radiation would of been detected by now.