The confession of Pakistani nuclear weapons scientists that they sold nuclear weapons technology to North Korea has become even more of a mystery. When Pakistan tested a number of nuclear weapons in 1998, American aircraft collecting air samples near the tests found evidence of plutonium. But Pakistan only built uranium bombs. But North Korea was trying to build a plutonium bomb. Pakistan denies that they tested a bomb design for North Korea. But Pakistan has had to reverse itself on such statements in the past.