ST. LOUIS (AP) — Fire officials say smoke from a massive warehouse fire in south St. Louis is considered hazardous.

Up to 100 firefighters have been battling the fire at Park Warehousing Services since about 10:30 a.m. Wednesday. KSDK reports a warehouse employee and a firefighter were hospitalized for smoke inhalation.

St. Louis Fire Capt. Garon Mosby says the smoke is considered hazardous and he urged area residents and nearby hospitals to shut off their heating and cooling systems and to stay inside. He declined to say why the fire was deemed hazardous.

The warehouse contained 150,000 citronella candles, car seats and Styrofoam products.

Smoke from the fire could be seen from miles away and flames were visible from Interstate 64, several blocks away.

The cause of the fire is not known.