The alarm was raised when the boy failed to come home to his mother after an evening out with friends in Stockholm. He was last seen at 2 am on Sunday outside a 7-Eleven store in central Stockholm, and the last known call from his mobile was made at 2.18 am.
Police are now trying to trace any further calls or text messages to or from his mobile.
“We intend to go through all calls and hope to trace some movements that we can follow up,” said police spokesman Kjell Lindgren.
On Monday evening the search moved to Värmdö, a suburb of the capital, after a member of the public who had seen a photo of the boy in the press called the police. The witness claimed to have seen a person resembling the missing boy outside Gustavsberg early on Monday.
On Tuesday morning police had still not found any trace of the boy, and were due to decide whether to continue their search.
Jackie Moberg at the police youth unit said it was normal for young boys and girls to disappear.
“But it’s only a few times a year that they are gone this long, and then you start to worry that something has happened,” said Moberg.