A four-alarm fire ravaged a partially built North County condominium complex Thursday, gutting a cluster of four-story frame structures and prompting widespread downtown evacuations and street closures, but no one was hurt.The blaze began spreading through the sprawling construction site at Escondido Boulevard and Woodward Avenue shortly before 2 p.m."There were workers on scene, but they all got out safely," fire department information officer Carol Rea said.At a late afternoon briefing, Escondido Fire Chief Vic Reed confirmed that the conflagration had not injured any civilians or emergency personnel.The cause was under investigation, with federal agencies -- including the FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives -- already on scene to aid local officials in the probe, Reed told reporters.The wind-stoked flames were visible from as far away as Vista, miles to the northwest, as the inferno quickly engulfed the structures under construction near the California Center for the Arts and Grape Day Park.Escondido resident Tim Prince described seeing the early moments of the fire, when just one of the towering wooden frameworks was ablaze."It was engulfed in flames," he said. "The flames (then) just jumped over to that other building."Several times, it appeared that the fire had been extinguished, but it kept "flaring up," Prince recounted.Another witness, Major Harbour of Oceanside, said the blaze was leaping 70 to 80 feet above the buildings as if "shot by a flamethrower.""It seems like it spread really fast," Harbour added.Crews quickly realized that their job was one of striving to keep the flames from spreading, Reed told reporters."Our immediate objective when we arrived on scene was to try to put enough fire engines on the corners to contain the fire to those specific two structures," the chief said.That task proved impossible, however, due to the danger of getting close enough to drown the interiors of the blazes."They were at such a stage of burning that we felt the potential for the buildings to collapse outwards, and we didn't want to subject the firefighters to any possible harm," Reed said.Blowing embers also started small blazes that damaged businesses in the area, according to broadcast news accounts.Emergency personnel evacuated the surrounding area, including a Rite-Aid store, a movie theater and numerous other commercial establishments, and shut down nearby roads as the firefight continued.The roughly 100 personnel battling the blaze had the flames contained by about 3 p.m., according to the fire chief."We don't have extinguishment yet, and we probably will not likely have extinguishment well until tomorrow or maybe the following day," he said in the late afternoon. "We have a lot of rubble in there, and it's burning underneath."Among the roadblocked routes were Centre City Parkway from Mission Avenue to Valley Parkway, the California Highway Patrol reported.Six truck squads and 25 engine crews responded to the fire, Reed said. Aiding Escondido companies were personnel from Carlsbad, Deer Springs, Del Mar, Oceanside, Poway, Rancho Santa Fe, San Marcos, Solana Beach and Vista.The gutted project was to feature 122 condominiums selling for roughly $400,000 to $450,000 each, Reed said.Click here to look at the buildings that caught on fire.