FLINN SPRINGS (CNS) – A fast-moving wildfire blackened hundreds of open acres near Lake Jennings Tuesday, forcing evacuations of some back-country homes and prompting a full closure of a several-mile stretch of nearby Interstate 8. The blaze erupted for unknown reasons alongside the freeway near Olde Highway 80 in Flinn Springs shortly before 2 p.m., according to Cal Fire. Within about two hours, the flames had blackened roughly 400 acres while spreading to the southwest and were posing an immediate threat to five homes, the state agency reported. Authorities directed those living along View Side Lane to clear out of the neighborhood while ground and airborne firefighters worked to corral the blaze. County officials also issued an “evacuation advisory” for Peutz Valley and the northern end of Harbison Canyon in the Hunter Pass area, alerting residents of those locales that they might have to vacate if the blaze kept moving in their direction. Temporary shelters for evacuees were established at Granite Hills High School on East Madison Avenue in El Cajon and at Joan MacQueen Middle School on Tavern Road in Alpine. The CHP, meanwhile, shut down I-8 between Tavern and Lake Jennings Park roads as a safety precaution. The closure resulted in gridlock for miles to the east and west. By 5 p.m., crews had halted the spread of the fire, allowing for the reopening of the westbound lanes of the interstate in the area, according to Cal Fire. It was not immediately clear what sparked the blaze.