4 Firefighters Hurt as 5-Alarm Blaze Strikes Office Building : Disaster: Fire departments from county, four other cities join in fighting Santa Ana blaze of unknown cause.

Four firefighters were injured Sunday night battling a five-alarm blaze that blackened part of a two-story office building.

One Santa Ana firefighter was treated for smoke inhalation and released. The nature of the injuries to the other three was not known late Sunday.

The fire broke out about 7:45 p.m. at Risi Plaza, a glass-and-concrete office complex at 600 N. Tustin Ave. Santa Ana Fire Department spokesman Karl Ellman said an occupant of the building called 911 to report smelling smoke and seeing flames before fleeing the building.

The cause of the fire was still under investigation Sunday, and the identity of the caller was not immediately known. Although hot spots were still visible inside the building at 10 p.m., most of the fire was extinguished.

“When we came out about 8 p.m., the smoke was very, very intense, just billowing out,” said Ruth Stingley, a resident of the neighborhood who watched the firefighting effort from across the street. “We could see a lot of flames but it seemed the Fire Department had it under control pretty quickly.”

Ellman said the fire broke out in the southwest corner of the building near the street. Three of the firefighters were injured when the second floor gave way, sending them tumbling below.

The fire was so intense that it was rapidly upgraded to a five-alarm blaze, the maximum classification for a fire, Ellman said. About a dozen fire engines raced to the scene from the Orange County Fire Department and departments in Costa Mesa, Fountain Valley, Westminster and Newport Beach, although not all were used.

Jay Gulko, 38, who lives in the Village Apartments complex across the street, was among scores of bystanders who gathered to watch the massive firefighting effort. He said he saw flames “leaping out of the roof” of the building.

Gulko watched as the firefighter who was later treated for smoke inhalation was hustled out of the building and tended to by his colleagues.

“He came out of the building and fell down on his knees in the street,” Gulko said. “They came and took him over to the grass for his comfort.”

Ellman said the extent of the damage to the building was not immediately known.

Times staff writer Jerry Hicks contributed to this report.