ARCADIA, Calif. (AP) — Crews are on the scene of a small but growing brush fire northeast of Los Angeles near communications towers and the historic observatory on Mount Wilson.

Los Angeles County officials say no structures are immediately threatened by the blaze that broke out before dawn Tuesday on steep hillsides in the Angeles National Forest.

Crews are aided by light winds and cool morning temperatures. Helicopters began making water drops after the sun started rising.

The blaze was initially estimated at around 5 acres, but it steadily expanded as flames chewed through dry brush.

The glow of flames is seen across parts of Los Angeles and surrounding valleys.

The fire's not burning near foothill neighborhoods but firefighters will try to protect the communications center and observatory near the 5,710 foot (1,740 meter) peak.