Criminal gangs have become increasingly refined in their quest to break into Swedish homes. By rifling through the coat pockets and bags of Swedish schoolchildren, thieves can put their hands on both keys and mobile phones.
The criminals can then use information on children's mobile phones to help find their home address and use the keys to let themselves in and carry out their robbery.
Police in Stockholm have surveyed around 40 reports of lost keys during the spring, and 22 resulted in a robbery.
"My advice is to change the lock and go through the home as soon as someone in the family loses their keys," Tony Roshage of the Stockholm police told the Dagens Nyheter (DN) newspaper.
In addition to stealing keys from children's belongings during the school day, burglars have also targeted school employees.
In one case, after stealing a staff member's home and car keys, thieves were able to use the licence plate number from an employee's car to find the address to which the vehicle was registered.
Because the burglars use stolen keys to enter their victims' homes, the robberies often go undiscovered for some time until someone realises that something is missing.
Roshage also warned that similar tactics could be employed at any public place, such as a swimming area or athletic field.
"Always keep an eye on your things and be careful about writing where you are using social media. Facebook is like candy for thieves," he told DN.