AFAIK it's still under investigation, so everything is pure speculation.
The South Bend TV station had this to say about the derailment: http://www.wsbt.com/news/local/59835427.html
Here is a quote from a local resident, "I was just down there being nosy along with everyone else in town (hey, it's Union Mills what else do we have to do?). It looks like about 15 double stack loaded container wells derailed at the crossover just east of the diamond at Wellsboro. Both CSX mains are out and with the signal damage CN trains are stopping and walking through the diamond. Cranemaster and at least 2 divisions from Hulcher are on scene as are hazmat and homeland security. Several of the railcars look to be damaged beyond repair and containers are being loaded onto an increasing line of semi trucks that are waiting. When I left six semi loads of panel track one trucks out of Ohio had arrived. There are several CSX trains stopped east and west of Wellsboro so when things finally open up it should resemble a parade for a quite a while.