A spokesperson for the police in North Rhine-Westphalia said on Friday that the men were suspected of having deliberately set light to a mattress.
Around 30 residents of the home were taken to hospital after the blaze on Thursday. One of them was seriously injured.
A further 24 people were treated at the site of the fire.
Fire crews were able to put out the fire on Thursday evening.
The fire had broken out at the former military barracks in Hövelhof-Staumühle on Thursday afternoon.
Around 500 people had been housed in the building. But it was almost completely destroyed by the flames.