Unless the equipment was put in the trailer red hot from hard work, we've all done that a million times without problems, it has to be electrical. Other possibility could be someone flipped a butt and logged itself somewhere unseen and it was exposed to fumes. I hate this for you, loosing equipment is the last thing I'd want to go wrong with my business.
Quick 32,36,& 44 Dually's
Ferris Evolution 27 Kaw 48"
DR Brush Mower
Toro Dingo 222
ISEKI Diesel Compact Tractor, attachments (bush hog, middle buster plow & land leveler
Steiner all wheel drive Tractor, attachments (stump grinder, rough cut mower, scrape blade & dual wheels)
5X10 open trailer
16' equipment trailer
1997 Ford F-350 7.3 4X4 SRW Crew Cab 8' bed