Officials are still investigating the cause of the massive fire at a 5,000 square-metre refugee centre on Tuesday that forced some 130 people to be evacuated and left another 30 refugees and rescue workers suffering from smoke intoxication.
Police said there were no serious injuries.
Six men, who were living at the home, have been taken into questioning over the fire, Düsseldorf police confirmed to The Local on Wednesday.
Police are investigating it as a case of serious arson and said there is no evidence of xenophobic motivations.
Local newspaper Express reported that police had found two of the men under investigation after one of them boasted about starting the fire to an Express journalist, saying it was out of frustration with the circumstances of their accommodation.
The other man showed a reporter a video of the flames spreading quickly.
Düsseldorf police told The Local they could not confirm any outside reports.
Officials have also said that for now the city will not take in any further refugees.
The fire on Tuesday was so large that the black billows of smoke could be seen rising above planes flying to and from the nearby airport.
Police said the some 282 refugees who formerly resided in the centre were placed in other housing. The burned-out building is set to be fully demolished on Wednesday.