Some 13 percent of all migrants who officially entered Germany in 2015 never turned up at the accommodation provided for them, Süddeutsche Zeitung reported Thursday. The news comes as Berlin tightens up laws on asylum seekers.

The newspaper’s report is based on Germany’s Federal Interior Ministry’s official response to a request filed by the Left Party. The ministry provided two explanations for the phenomenon: the refugees either continued their journey to another European country or choose to live illegally within Germany.

According to Frank-Jürgen Weise, the head of Germany's Federal Office for Migration (BAMF), there are as many as 400,000 asylum seekers within the country who have no ID documents and German authorities have proven unable to identify them, the head of the BAMF agency said in Berlin on Thursday.

Last year, Berlin was unable to expel all illegal aliens to the country responsible for them, which according to the Dublin Regulation is the EU state a refugee first entered.

Only one in 10 asylum seekers was returned to the country from

which they entered Germany, and in 2014 it was one in five refugees.

The reluctance of other European states to take back the refugees is understandable: Greece alone has witnessed a 21-fold growth in immigrants in one year.