A Swiss centre for processing failed asylum seekers had claimed to have lost track of 60 percent of the 649 migrants awaiting deportation who they say have simply disappeared.

From March of 2017 to June of this year 649 failed asylum seekers have been sent to the Embrach referral centre located in the canton of Zurich, but officials say that 309 of the failed migrants have simply disappeared and authorities have little to no idea where they may have gone, 20 minutes reports.

The centre is meant to be the final step for failed asylum seekers before they find out whether they will be sent back to another European country as per the EU’s Dublin regulations, or back to their home country.

The State Secretariat for Migration confirmed that around 500 of the migrants had departed the centre altogether, with the government losing track of 309 of them.

Remarkably, very few countries actually detain failed asylum seekers scheduled for deportation prior to expelling them, allowing many to go underground — or even carry out terror attacks, as in the case of Anis Amri in Berlin and Rakhmat Akilov in Stockholm.

Failed Asylum Seeker Causes Airport Chaos, Flights Grounded https://t.co/3vGZDcrONy — Breitbart London (@BreitbartLondon) November 14, 2017

Failed asylum seekers going underground has happened across Germany throughout the migrant crisis. In February of 2016, the German Federal government was forced to admit it had lost track of over 130,000 asylum seekers following a parliamentary question from the far-left Die Linke party.

Other countries have reported similar cases, with Finland admitting last August — just days after an Islamic extremist failed asylum seeker had stabbed several people in the city of Turku — that they had lost track of around 5,300 migrants.

Finnish interior minister Paula Risikko said that while she thought many may have gone back to their countries of origin, others could have used the Schengen open borders agreement to infiltrate to another European country.

In some cases, asylum seekers have escaped from more well-guarded deportation centres, as in Hamburg last November.

In that case, a 24-year-old Albanian failed asylum seeker fled the Hamburg deportation centre, located at the airport, and caused flights to be diverted and others grounded, due to fears he was at large on the runways.