The European police intelligence or Europol said that over ten thousand migrant children may have disappeared after arriving in Europe over the past two years, adding that minors had vanished after registering with state authorities.
Police have warned that children and young people may be forced into sexual exploitation and slavery by criminal gangs.
Officials in Italy reported in May 2015 that an estimated five thousand children had disappeared from asylum centers in less than a one year period.
Sweden also reported in October that at least one thousand refugee children and young adults had gone missing in Trelleborg.
A Europol spokesman said that they believe many who have landed in Greece have also gone missing and warned that gangs known to be involved in human trafficking in Europe are now targeting refugees.