The incident prompted the evacuation of the building on West Sherman Way, near Costello Avenue, shortly after 10:30 a.m., a spokesperson for the Los Angeles Fire Department said.
One patient was transported to Mission Community Hospital in Panorama City in unknown condition, and two others were taken to Valley Presbyterian Hospital with minor injuries.
A hazardous materials team was summoned to the scene. Authorities say the incident involved some form of cleaning solvent in the kitchen area at the Metapan restaurant.