An Apple site in Spain reports that the National Police arrested five employees at the Amazon logistics center in Madrid accused of stealing 500,000 euros (US594,000) worth of iPhones.  

At the time of the arrest, the detainees had 10 iPhones in their possession , as well as a large number of stickers with the IMEI of various devices. It appears that the detainees tore the codes from the boxes to make the investigation by the police more difficult. IMEI stands for "International Mobile Equipment Identity" which is a number, usually unique in identifying 3GPP, iDEN and satellite phones.

Amazon began an internal investigation when they detected that there were certain packages whose weight did not match the registered one. That's when he decided to place hidden cameras to see if anything strange was happening.

After their investigation they passed the case to the police who have ended up arresting these 5 people. For more on this, read the report from iPadizate here. Note that you'll need to translate the article.