SAN DIEGO (FOX 5/KUSI) — Cal Fire crews are battling a brush fire that erupted on Otay Mountain Thursday afternoon. The fire, which has been named the "Border 2 Fire," was reported after 2:15 p.m. in the area of Otay Mountain Truck Trail in the Otay Wilderness Area. According to Cal Fire, it is currently 600 acres as of 8:13 p.m., but has a "dangerous rate" of spread. It remains 0% contained Thursday night. The fire jumped from 350 to over 500 acres within a half hour at one point. No structures are believed to be threatened at this time, although there are a few transmitters used by U.S. Customs and Border Protection on top of the mountain and several structures at its base — including two detention centers. The fire caused a massive plume of smoke to blow from the mountain. Due to the Santa Ana winds, the smoke appeared to be moving west, over Otay Mesa and Tijuana. “The way it spread in the last couple hours," Christian Trip, a local resident, said as he watched the flames burn down the mountain. "Even two, three hours ago, it was tiny and now look at this. It’s surreal.” A smoke advisory has been issued by the San Diego County Air Pollution Control District for communities in the southwest of the county. The smoke is expected to continue blowing west through Friday morning, the district adds, with winds weakening overnight. "In areas where you smell smoke it is advised that you limit physical/outdoor activity," the district said. "If possible, stay indoors to limit your exposure to fine particulate matter and ozone, especially those residents with respiratory or heart disease, the elderly, and children." Around 6:23 p.m., the San Diego County Sheriff's Department announced the closure of Alta Road, located just south of Otay Mesa Road. The public is asked to avoid that area until further notice. In a post on X, Chula Vista fire officials are monitoring the fire. While smoke is visible, they say it does not pose an immediate threat residents at this time, although residents are advised to take precaution going outside due to the smoke impacting air conditions. "Extra officers are stationed around the city to monitor and assist if evacuations are needed. This is precautionary and not cause for alarm. Use 9-1-1 for emergencies only. For non-emergencies, call (619) 691-5151 or report online via ACT Chula Vista," the City of Chula Visa said in a post on X at 6:14 p.m. The city also closed all parks and recreation centers early Thursday over the air conditions. More than 200 firefighters responded to the blaze, naming the strong winds, low humidity levels, and dry vegetation as fuel for the flames. Photos captured from fires in La Jolla, Otay Mountain “The brush and the vegetation throughout the county spent all summer long drying out, and we have not had any measurable rain this rainy season,” Cal Fire Cpt. Robert Johnson said. While the area is seeing a below average water year so far, rain is expected Sunday. That usually can cause mudslides or flooding in burn-scarred areas, but Johnson says because of the location of the Border 2 Fire, he doesn’t expect that to threaten any structures once they put out this wildfire. “The rate of spread of this fire and the fire conditions is not abnormal for this area," Cal Fire Captain Robert Johnson said. "What is abnormal is that we’re experiencing these conditions in the month of January.” The fire is one of two that sparked almost simultaneously at different parts of the county as high winds continue to lash the region. The second ignited in La Jolla, prompting emergency officials to issue evacuation orders for nearby areas. All orders have since been lifted. Much of the county has been under a Red Flag Warning throughout the week for conditions that could create critical fire risk, given continued arid weather and Santa Ana winds. According to the National Weather Service, wind speeds in the area of the Border 2 Fire were recorded of 28 miles per hour, with gusts up to 38 miles per hour. Meanwhile, relative humidity was placed around 6%. Fire crews were quick to put out a number of potentially dangerous fires throughout the week, including several that burned outside the boundaries of the area under a Red Flag Warning. The pair of brush fires brought the total number of blazes to erupt to three on Thursday alone. This is a developing story. Check back for updates.