Update:
According to Spanish police:
Ingrid and Lodewijk apparently got killed in the appartment of one of the 3 arrested men. After that their bodies have been buried.
The police presumes the murder is apparently related to a business-conflict; they knew the 3 men from the past.
http://www.telegraaf.nl/binnen…_in_flat_vermoord___.html
Ingrid and Lodewijk stayed for two days in the appartment, so there was no kidnapping before..
http://www.ad.nl/ad/nl/13407/V…-door-oude-bekenden.dhtml