Under hood fuse block melted

[Bplante]

Hey I own a 2015 Silverado 1500wt I recently had my fuse block under the hood melt. It’s currently at the shop. Anyone seen this before. 
 

I used my truck on Sunday. Parked it with my enclosed trailer (only has driving lights no power inside) attached and plugged in. Noticed on Monday night the radio screen was lit up but it was pouring rain I just figure the system would cut the power if it was something left on. Forgot about it on Tuesday and then went to start Wednesday morning with no start. (Seemingly battery went dead). So I charged up the battery. Still got the same issue. Upon checking for blown fuses I noticed the starter relay and fuse were both blown/caught fire. I tried switching out the fuse and relay and nothing. Being stumped I sent it in to the shop and this is what they sent me for pictures. Say I need new battery and new fuse block but they do not know what caused this. 
 

Battery charger was connected properly can’t find any rodent damage. 
truck did sit from Sunday night to Wednesday morning before being attempted to start 
 

many help would be great. 

[miraza13]

I just had the same issue, what was the cause?

[Carroll Hardesty]

My 2014 Silverado fuse box caught fire  about 7/8.Still in shop.Between getting parts  and finding someone that knows how to fix,it is still in shop with no end in sight.

First problem I ever had with a 5.7l,I have had 3.

   If I didn’t have a fire extinguisher and something to pry the battery cable off it would have burned up