"We assume these are doing something completely different, that they work rather than study," said Michael Parzyszek of the EU border control agency Frontex to Sveriges Radio (SR).
A report carried out by the Swedish Migration Board suggests that up to one third of students who are granted resident visas in Sweden do not show up for class and are getting away with it because the rules are so slack and controls are so rarely undertaken, according to SR.
Sten Alstander at the Swedish Migration Board admits that his organisation is powerless to stop the widespread abuse of the system, which could involve several thousand students.
"No sadly, that is the way it has happened. It hasn't been our responsibility to check and no other agency has shouldered it either," he told SR.
Some 15,000 people arrive every year with a one-year visa that allows them to study in Sweden.
Up until now all you needed to obtain a residency permit was a letter of admission from a college, as well as proof that you have enough money to survive in Sweden during the study period and to pay an application fee of about 1000 dollars.
There are very few checks to see if they actually spend any time at all in their allotted colleges, while many instead find work, the report claims.
The last time any kind of investigation was carried out by authorities, it showed a similar result, that some 25% were not showing up at college. Nothing has been done since to tighten up the rules.
However the situation may change.
Starting this autumn, the system of tuition fees will take effect in Sweden for foreign students.
For the first time colleges will have to report students who do not turn up for classes to the immigration office, which will then have the power to revoke the permit.
However, according to the Migration Board, the students will still only have to attend and pass studies comprising ten weeks out of the 40 week academic year to qualify for a permit.