Paramedics responded to the 24300 block of South Western Avenue in Harbor City, where the incident was reported. It's unclear what the substance was, but it was possibly inhaled, fire officials said.
It was first reported that there were as many as four patients, but fire officials later confirmed three people were transported by LAFD ambulance to an area hospital with non-life threatening illnesses.
The ages of the patients were not immediately known, and it's unclear whether they're connected to the school.