German police special forces have stormed a hangar at Berlin's defunct Tempelhof airport, which now houses Berlin's biggest refugee accommodation centre, according to German magazine Focus.
It comes hours after a truck ploughed into a crowd at a Berlin Christmas market on Monday evening , killing 12 people and injuring 48 others.
Four young men were questioned at the police station in the refugee camp, but there were no arrests, according to Sascha Langenbach, spokesman for the refugee agency.
The operation, which also involved forces from the special unit (SEK), began at 3am and lasted five hours, involving up to 250 officials, Welt.de reported.
Police have detained a migrant in relation to the incident, which they are now investigating as a "suspected terror attack" that deliberately intended to cause harm.
“Our investigators assume that the truck was deliberately steered into the crowd at the Christmas market at Breitscheidplatz,” police said on Twitter.
“All police measures related to the suspected terrorist attack... are progressing at full steam and with the necessary diligence.”
They believe the man arrived in Germany in Ferbruary as a refugee from either Afghanistan or Pakistan, the German newswire DPA reported on Tuesday, citing unnamed security sources.
