Interior Minister Claude Gueant says an unextinguished candle was behind the blaze reported shortly before dawn Wednesday in the city-owned building in the Paris suburb of Pantin.

A ministry official, speaking on condition of anonymity because he was not authorized to speak publicly on the matter, said the six were believed to be Tunisian and Libyan nationals. An investigation is under way.

After visiting the site, Gueant criticized “truly criminal” networks that bring in illegal migrants, fan their hopes of a better life — then dump them.

France’s conservative government has taken a tough stand on illegal immigration.