A brush fire burning on a brush-covered ridge between the city of Los Angeles and suburban Glendale has grown to about 40 acres.

Los Angeles fire spokesman Devin Gales says an unknown number of homes are potentially threatened in the Eagle Rock area near the interchange of State Route 134 and Route 2.

A Glendale fire official says voluntary evacuations are under way and there are discussions about making the move mandatory.

Helicopters are making water-dropping runs on the blazing slopes of the Verdugo Mountains. Winds are light but temperatures remain in the 90s.

Gales says there were three other spot fires in the same general area.