My guess would be gas. If a small gas leak then just switching on a light could cause a small spark and ............well the pictures speak for themselves.
Take care All.
Edit: Google translation of report:
Starnberg - In a mobile home in Starnberg, an explosion occurred on Monday evening. A man was flown away with a rescue helicopter, the mother and child were easily injured.
On Monday night, around 9 pm, a severe accident occurred in a forest in the south of Starnberg. In a mobile home an explosion or a deflagration occurred. By the force of the explosion, the roof of the VW bus was folded backwards, the sliding side door slammed about ten meters into the forest, and all the doors and the interior furnishings were badly damaged.