Southern California's Alisal Fire is 50% contained

Part of the Alisal Fire burns in California's Las Flores Canyon on Friday afternoon.

(CNN)Southern California's Alisal Fire, which earlier this week closed portions of US Highway 101 and the Union Pacific Railroad west of Santa Barbara, was 50% contained as of Saturday morning, fire officials said.

That's an improvement from Friday morning's 41%. The fire has burned about 17,200 acres since it started Monday afternoon, according to InciWeb, a US clearinghouse for wildfire information.
    The closed portions of the highway and the railroad have since reopened.
      The flames earlier this week also neared but missed the Santa Barbara area's famed Reagan Ranch, known as the Western White House during the Ronald Reagan administration.
        The majority of the fire's recent growth has been on the western flank, toward the oceanside community of Gaviota, according to InciWeb. High temperatures and low humidity have contributed to the growth, it said.