The German AAIB published a press release today regarding this accident:
Bundesstelle für Flugunfalluntersuchung - Homepage - Pressemitteilung zum Unfall mit einer Piper PA32 am 27. August 2013 in der Nähe von Arnsberg
It contains a somewhat cryptic statement according to which
"The tanks in both wings and the fuel lines were damaged. Fuel was not found"
Which could be interpreted to mean that fuel was neither found in the tanks nor at the crash site, thus implying that the aircraft ran out fuel.
One of the children (16 months old) is still hospitalized with life-threatening injuries.