"We have 27,991 people with student loans outside the country who owe us money," said CSN spokesman Magnus Forss.
"Together they owe 3.3 billion kronor ($430 million). It's most regrettable," he told Metro.
For the past two years CSN has been using the services of debt collection agency Intrum Justitia. The company has been tracing addresses of people who owe money to CSN and who live abroad. CSN does not have contact details for nearly 19,000 former students.
The organization is currently focusing its efforts on former students in the Nordic countries, Britain and the United States.
CSN must succeed in recovering debts before the borrower reaches the age of 68. At that age, unpaid student debts are cancelled.