A quickly moving 100-acre wildfire in Norco, Calif., in Riverside County forced the evacuation of 1,500 residents Tuesday, threatening an estimated 500 homes, according to Cal Fire.

The Mann Fire was first reported at 9:41 a.m. in the Santa Ana River Bottom near California Avenue, authorities said. There was no containment by the time authorities announced mandatory evacuations shortly before noon.

Cal Fire Capt. Fernando Herrera described the blaze as wind-driven and told KTLA it was spreading at a rapid rate. He said of the roughly 1,500 residents affected, at least two people have been treated for smoke inhalation.

The National Weather Service reported just before 11:30 a.m. that winds in the area were gusting at 15-25 mph, with humidity at 10-15 percent.

But Herrera said winds became lighter as the afternoon wore on.

Around 1 p.m., he told KTLA they appeared to be blowing 5-10 mph after being much stronger when the fire broke out before 10 a.m. He estimated they were about 30-40 mph at that time, driving the flames forward.

According to Herrera, the roughly 210 firefighters battling the blaze were focusing their efforts on protecting homes in densely populated neighborhoods located north of the river bottom.

By 2:30 p.m., Cal Fire officials said the fire still had no containment after burning 100 acres.