A fast-growing wildfire that broke out early this morning in the mountains above the Los Angeles suburb of Glendora has grown to more than 1,700 acres, burning at least one home and prompting evacuations, authorities said.

Reported just before 6 a.m., the fire sent a huge plume of smoke into the air as it advanced south down hillsides and threatened at least two homes and other structures, aerial news footage showed.

The Los Angeles County Sheriff's department announced mandatory evacuations for areas west of Glendora Boulevard to North Sierra Madre Boulevard.

Meanwhile, local radio station KFI-AM was reporting just after 9:30 a.m. that Glendora Police had confirmed detaining at least three individuals in connection to the fire.

A police alert "strongly" recommend evacuations for residents living between Grand and Glendora Mountain Road, north of Sierra Madre. Several schools were reported closed, as well as Citrus College. But other schools, like Glendora High School, remained open.

A later report by KFI-AM news reported ash from the fire was on the verge of reaching Catalina Island, about 30 miles off the California coast and about 75 miles from Glendora. As the smoke covered vast portions of the Southern California sky, the sun shone through the haze in bright red.

Approximately 500 firefighters, including County crews alongside Forest Service responders to fight the blaze, as water-dropping helicopters attack from the air.

Miguel Orneals of the Los Angeles County Fire Department said his agency was requesting more equipment for structure protection because the blaze, fueled by excessive dry conditions and Santa Ana winds, was threatening residences and homes.

Angeles National Forest spokesman Nathan Judy told KTLA-TV at about 7:15 a.m. that the blaze had grown.

"Our fuels are very dry, they've been that way all year," Nathan Judy, Angeles National Forest spokesman, told KTLA-TV.

As the flames advanced down the hill earlier in the morning, authorities warned residents to prepare to leave at a moment's notice.

"If you feel uncomfortable, if the hairs are standing up on the back of your neck ... just go ahead and evacuate," Judy also said in his interview with KTLA. "Let us do our jobs and take control of this fire and then you can come back in."

The fire hits just as the National Weather Service extends red flag warnings for Los Angeles and Ventura counties until 3 p.m. Friday, warning of very low humidity worsening already tinder-dry conditions.