SAN JOSE -- Firefighters spent Monday morning putting out hot spots on a five-alarm blaze that destroyed a former television news studio near downtown as arson investigators waited to get inside and begin their work.

Fire officials say as many as 30 homeless people occasionally stayed in the vacant building overnight but they were unsure if anyone was trapped inside. Some of the homeless people who stayed in the former KNTV-11 building on Park Avenue told firefighters everyone got out safely, but fire officials won't be sure until they search the rubble, fire Capt. Cleo Doss said.

As of 10:30 a.m. Monday firefighters were still dousing water on hot spots and waiting for the building to "cool off" until allowing arson investigators to go inside, Doss said. The fire ignited at about 3 p.m. Sunday and quickly grew to five alarms.

Firefighters attempted to get inside to look for people, but the flames, smoke and heat drove them back.

Two people, apparently homeless individuals, got out of the building safely by the time firefighters arrived, according to fire Capt. Reggie Williams.

The fire was so large the cities of Santa Clara and Sunnyvale sent ladder companies to help the San Jose Fire Department. In all, about 100 firefighters were needed to extinguish the blaze.

The cause of the blaze is under investigation but firefighters are treating it "like a crime scene until we can prove otherwise," Doss said.

As five ladder companies poured thousands of gallons per minute onto the fire, dozens of onlookers, residents and news reporters gathered at the corner of Park and Montgomery Street and at a few more vantage points. More than a few onlookers took photos and posted the images on social media.

Luckily, Williams said, firefighters were familiar with the building. It sat across the street from the department's training facility. In 2012, the KNTV building -- vacant since 2004 -- was also used for fire training.

The building was purchased by the city of San Jose's Redevelopment Agency in 2008 during its efforts to purchase land in the downtown area for a prospective baseball stadium, according to city spokesman David Vossbrink.

The property remains publicly owned.

Two firefighters suffered minor injuries and were treated at the scene and released, Williams said.

Ray Bramson, the homelessness response team manager for San Jose, said the vacant building has been on the city's radar as a place where transients would sometimes stay. But Bramson said outreach workers from one of their non-profit partners visited the site last Tuesday, and there was only one woman found outside the building.

"That person said that everyone had moved on," he said. "The building was secure and boarded up."

But the reality, Bramson added, is that any empty or abandoned building is potential shelter for the homeless.

"People do break in and try to live in these sites," he said. "We've got 5,000 people in our city who on any given night who are looking for places to stay."

And while outreach workers regular visit homeless encampments, they do not enter fixed structures.

"We can't send our outreach people into abandoned buildings because it's not safe," he said.

Anyone with information about the fire may call the San Jose Fire Department at 408-277-8952.

Staff writer Joe Rodriguez contributed to this report. Contact Mark Gomez at 408-920-5869. Follow him on Twitter @MarkMgomez.