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Nick Ut, Associated Press
State highway workers watch as Los Angeles firefighters work to put out a massive fire along State Route 110 that engulfed an apartment building construction site near downtown Los Angeles on Monday, Dec. 8, 2014. Crews battled two large fires in Los Angeles early Monday, including one downtown that closed portions of two major freeways and blanketed the area in ash and heavy smoke.

LOS ANGELES — Two raging fires in Los Angeles destroyed a massive residential complex under construction, heavily damaged a building undergoing renovations, and snarled rush hour traffic while raining ash over a large area early Monday.

More than 250 firefighters fought a downtown blaze that was sparked at a block-long construction site around 1:20 a.m., Los Angeles Fire Department Chief Ralph Terrazas said. Flames visible for miles consumed the 7-story wood-framed structure and damaged two adjacent high-rises before being brought under control within 90 minutes.

"The radiant heat was strong enough to burst windows in one building next door," Battalion Chief Joseph Castro said.

Three floors of that adjacent building were damaged by fire and several other floors sustained water damage. The building, which houses city offices, was closed for the day.

Embers spewed from the fire landed across a freeway, igniting brush and charring a traffic sign. But fortunately winds were light and did not blow the fire even farther.

Portions of U.S. Route 101 and Interstate 110 were shut down for a time over fears that debris might fall into lanes. The northbound 110 remained closed after sunrise, as commuter traffic backed up for miles.

No injuries were reported. The burned structure was planned to be a residential building. The site was still smoldering by midmorning and downtown was littered with ash.

Shortly after 4 a.m. another large fire was reported at a mixed-use building about 2 miles to the west. More than 100 firefighters from multiple agencies responded and had the flames under control in less than two hours, according to Chief Deputy Mario D. Rueda.

One person in a nearby apartment building was treated for minor smoke inhalation, he said.

Around 10 businesses were housed in the two-story building in the Westlake district, and portions of it were being renovated for residential use.

There were no indications the two incidents were connected, Terrazas said.