The downtown Los Angeles skyline pictured at night. The city’s urban center was the site of a massive blaze early Monday morning after a 7-story building that was under construction caught fire, Dec. 8, 2014. Creative Commons

Hundreds of Los Angeles firefighters battled a massive apartment fire in the city's historic downtown center on Monday, shutting down portions of two major freeways. The fire engulfed a 7-story apartment tower that was under construction on Fremont Avenue. The flames damaged two nearby buildings, including several floors of a 16-story office structure.

"This is a historic fire, what we as firefighters would call 'a career fire,'” David Ortiz, public information officer at the Los Angeles Fire Department, told NBC News. "It's huge. I really can't remember a building fire this big and I have been with the department for 13 years." Ortiz added that the building appeared to be “completely lost.” No injuries were reported.

The highway closures didn't seem to affect morning commutes much in the notoriously traffic-jammed city, with traffic on the 101 Freeway and the southbound 110 resuming around 4:30 a.m. PST. Officials hoped to reopen the northbound 110 by 8 a.m., the Los Angeles Times reported.

The apartment building, one of several upscale complexes to be built in downtown Los Angeles over the past 10 years as part of an effort to revitalize the city’s urban center, occupied an entire city block. The fire was fueled by the building’s wooden framework and was first reported around 1:20 a.m. Monday morning. The cause of the massive fire remains unknown. Investigators looked for signs of arson, however, officials told the Times it was “too early to make that determination.”

Los Angeles’ now-glitzy downtown district, once known for its urban blight, has undergone a transformation. Ten years ago, "it was so empty down here you could shoot a rocket down the street and not hit a thing," Rhonda Slavik, a consultant for real-estate research firm Polaris Pacific, told the Wall Street Journal in April. "Now, there are young people walking their dogs, families with strollers, restaurants teeming with people." Hundreds of boutiques and trendy eateries now dot the area as demand for luxury housing has soared.

Here are social media photos from Monday morning’s fire in downtown Los Angeles.