Dozens of firefighters were called to St James' Caravan Park on New Road, Featherstone, after flames took hold just after midnight on Monday.
Today Staffordshire Fire and Rescue Service said an electric blanket was responsible for the fire.
Fire Investigation Officer Tim Hollingworth said: "This was a tragic accident that may have been avoided. We cannot stress enough the importance of ensuring that your electric blanket is safe to use. The consequences of using older or faulty electric blankets can be devastating."
"All older or faulty blankets should be replaced.
"According to the Electrical Safety Council you should think about replacing your electric blanket every 10 years. It is important to get your blanket checked to make sure it is still safe to use – ideally this should be once a year by a competent electrician.
"It isn't just older blankets that can place you at risk. Folding electric blankets can sometimes damage the internal wiring, making them dangerous.
"If in doubt – throw them out. The risks just aren't worth taking."
Two crews from Cannock, one crew from Gnosall and two crews from West Midlands Fire and Rescue Service's Fallings Park station were called to the scene.
To book a free Home Fire Risk Check contact: 0800 0241 999.