Of the 21,748 people who have been given deportation orders by Sweden's Migration Agency last month – the largest number in history, by the way – 14,140 are registered by police as "departed" or "wanted," the Swedish website The Local reports.
"We simply don't know where they are," said Patrik Engström, the head of the national border police.
It is unknown how many of the missing are still in the country or may have left for elsewhere in Europe. The rest of the illegals are either in refugee centers, in custody, or living in separate accommodations they have arranged for themselves, awaiting deportation.
The Swedish government has previously announced it wants to step up efforts to ensure that people without the legal right to stay in Sweden exit the country. But police say most of its resources are currently devoted to carrying out ID checks after Sweden stepped up border controls.
"It's a huge task and it is completely dependent on the police being allocated resources," said Engström.
According to The Local, last year the proportion of those leaving the country voluntarily after an expulsion order was 41 percent. Some of the remaining numbers were forcibly deported, but in most cases the refugees went underground.
The Migration Agency said at the time that the vast majority of the "disappeared" were "Dublin Regulation" cases. Under that plan, refugees should be deported back to the first EU country they entered, often Italy or Greece. But if refugees can delay their re-applications by 18 months, they may be able to stay in Sweden - hence the motivation to go underground.