The Colby fire is threatening the residential community of Glendora in the San Gabriel Valley, just 25 miles northeast of downtown Los Angeles. Mandatory evacuations have been ordered as unseasonably warm weather, a year of dry conditions and the infamous Santa Ana winds have combined to spread the flames out of control.

News helicopters broadcast images of at least one house burning to the ground. Several hundred firefighters were on the scene, the Associated Press reported.

The fire is known as the Colby fire for the name of a trail near where it is believed to have ignited. The blaze started early Thursday morning and grew rapidly, awakening the neighborhood about 6 a.m., according to the Los Angeles Times. Two hours later, the fire had burned 125 acres, the newspaper reported.

The Azusa Police Department ordered residents north of Sierra Madre Boulevard and east of Azusa Canyon to evacuate. The Glendora Police Department announced earlier Thursday that three people were in custody in connection with the fire; no additional information was immediately available, and the department did not specify whether those individuals were under arrest.

The National Weather Service issued red flag warnings for areas of Los Angeles, Ventura, San Bernadino, Orange, Riverside and San Diego counties through Friday, indicating a high risk of fire. The service cited strong winds, with gusts of up to 40 miles per hour in the region’s valleys, low humidity and “historically dry fuels.”

Hundreds of firefighters work to contain a 125-acre brush fire encroaching on Glendora, Calif., a posh residential community near Los Angeles. (Reuters)

“If fire ignition occurs, there could be rapid spread of wildfire that would lead to a threat to life and property,” forecasters warned. The temperature in Glendora is expected to reach 86 degrees Thursday.