Hey trainwreck, check this one out. Happened today just about 30 miles west of me. Now I realise there really isn't enough pics to say for sure, but if you look at the pics, it seems to me that someone derailed this train. First, it was a section of track that had several switches. And just a short distance beyond derailment the train crosses a trestle bridge across the Tennessee River. As a matter of fact, when I crossed the river bridge this morning, I could see the stopped train already on the trestle bridge to the left. Once we got up the road a bit and reached a bridge on the highway that goes over tracks, I could see why it was stopped. My point is, the train would have been going at a low speed across the trestle bridge, a low enough speed that it appears (looking at pics) that someone "switched the tracks" as the train was passing. It's clear to see in the pics that train cars were on different tracks in two places. Hmm, seems someone was up to no good, who knows if they'll ever find out who did it. http://www.wbir.com/news/local/story.aspx?storyid=132232&odyssey=mod_mostread
This article says that it was 4 that jumped and hit 5 on another track. Train derails can have no good reason to happen and are just so unpredictable. http://www.volunteertv.com/news/headlines/101732698.html
Hmm, first of all, I'm in no position to argue the official statement from Norfolk Southern, but I know that area. There is no "yard". The tracks cutting off to the right go to Kimberly Clark plant. The two "parallel" tracks are for train siding for other trains crossing the trestle bridge. Those pics clearly show cars of the same train on the main track and siding track approaching trestle bridge. And switched in two different parts of train. trainwreck gave me the best alternative explanation while at chatroom; faulty track switch that would put cars on different tracks.
Atco, looks like a car "picked" the switch. Either the switch was worn, or a wheel was worn. Causing the car to pull onto the other switch, from there, over they go.