Published: Jun 02, 2013 10:31 AM EDT

LOS ANGELES (AP) - A fire that has burned at least five structures and is threatening about 1,000 others exploded in size overnight, burning dangerously close to two foothill communities north of Los Angeles.
 
Officials on Sunday morning said erratic overnight wind had fanned the fire in the Angeles National Forest to nearly 41 square miles.
 
Matt Corelli of the Forest Service told The Associated Press that five structures had been destroyed. He said they could be homes but crews were waiting for more daylight to make a positive determination.
 
Approaching flames triggered the evacuation of nearly 1,000 homes in Lake Hughes and Lake Elizabeth at the northern edge of the forest.
 
Crews working in steep terrain expected cooler weather Sunday after triple-digit temperatures a day earlier.
 
The fire is 20 percent contained.