The first fire damaged six apartments at a building at 86-16 60 Avenue in Elmhurst.
The Fire Department says it took nearly an hour and a half to get the fire under control. It spread among a group of two-story buildings sharing a roof. The cause was an unattended candle, officials said.
Hours later, fire and smoke poured from the roof of an apartment building at 16-66 Bell Boulevard.
Investigators said illegal use of a torch on combustible roof sparked this fire. Fire marshals arrested the building worker for reckless endangerment.
In both cases, more than a dozen firefighters suffered from heat exhaustion trying to put out the flames.