[heleny]

for damage control and recovery of incriminating evidence

Exactly.

Maybe now they even get to study the effects/results of whatever experimental explosive they might have had.

[menotyu]

I don't know what they used but it sure was effective. Before After

[JasonC]

It is not an experimental explosive. There are 3 realistic possibilities, in order of likelihood -

1. It was solid rocket fuel, from a cargo of missiles.
2. It was a collision, accidental, "fertilizer" etc.
3. We or a friendly intel agency blew up whatever was on the carriage (planted bomb e.g.)
4. Sub critical event from too much U-235 items getting too close to each other. (Uncontained, it blows apart the material and halts a chain reaction that way).

From previous reports, some important facts -

- "The station was destroyed as if hit by a bombardment and debris flew high into the sky," Yonhap said, quoting the unidentified Chinese sources."

- "North Korea appears to have cut international telephone lines to the area to prevent information about the explosion getting out, Yonhap added. The North appears to have declared a type of emergency in the area.

- The blast reportedly damaged structures up to 2 km away, other estimates say 1.5km. Most structures within 500 meters were leveled, including some apparently of brick or cinderblock. Some reports of debris up to 10 miles away. And there are conflicting reports of possible casualties up to 5 miles away. Reports of the depth of the crater say up to 15 meters deep.

- Initial media reports on the cause of the crash were clearly made up stories. The story has changed to explosion of stuff carried on some of the cars of one train. Satellite pictures of the craters show two distinguishable longish areas generally following the axis of the rail line.

My best guess is they were transporting missiles which blew up. But other causes can't be ruled out IMO.