Personnel with the Los Angeles County Fire Department responded to a brush fire that broke out on the 11900 block of West Sierra Highway in Agua Dulce on Monday afternoon and was quickly halted at 2 acres.   The blaze, nicknamed the Whitney Fire, broke out shortly before 5 p.m. with structures initially threatened and fire officials declaring it a second-alarm brush response.   Once the first units arrived on the scene, firefighters were able to get a handle on the fire and structures were no longer at risk, said Melanie Flores, supervising fire dispatcher with the L.A. County Fire Department.   The cause of the fire is unknown and under investigation, she added.   The fire was halted at 2 acres minutes before 5:20 p.m. and no injuries were reported.   The post Brush fire in Agua Dulce halted at 2 acres   appeared first on Santa Clarita Valley Signal.