By Susie Steimle

OAKLAND (KPIX 5) — The grueling task of determining what sparked a massive construction fire in Oakland is now underway.

More than 20 federal fire investigators are looking into the cause of the fire that broke out early Friday morning on Valdez Street.

The blaze forced hundreds of people to leave their homes and businesses.

One man is calling this fire a war on housing.

Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) investigators still haven’t been able to safely enter the structure since the fire started Friday.

They have yet to determine what caused the fire.

But nearby developers are convinced it’s arson and they aren’t wasting no time protecting their own construction sites.

It’s the fifth time ATF has been tasked with finding out what caused a brand new apartment complex to be destroyed by fire during construction in Oakland.

Arson victim Rick Holliday said, “I know what it feels like to have that happen, it’s a gut punch.”

Holliday owns 3800 San Pablo Avenue. That apartment complex was burnt to the ground twice by arsonists this past year.

While ATF is still unsure about the cause of the most recent fire, Holliday is convinced it’s the same story.

“I’ve always believed this is an arsonist…I said there was a war on housing during the last fire,” Holliday said.

Adding to his suspicion, Oakland Mayor Libby Schaaf asked him to help other developers protect themselves.

Holliay said, “…asked me if I’d be willing to join other developers to talk about how do we fortify ourselves against having more fires and how do we organize ourselves to best catch people doing this.”

No arrests have been made.

ATF released surveillance video of a suspect seen in the area of the San Pablo Avenue fire back in May.

ATF is also offering a $110,000 reward for information leading to an arrest in the three previous arsons.

Friday’s fire started at 4:30 a.m. and displaced more than 900 residents as hot flames scorched nearby businesses and forced firefighters to rip down a construction crane.

The complex would have housed nearly 200 apartments and a shopping mall on the bottom level.

Holliday said, “This is a terrorist group. I think it’s pretty obvious. They’re doing something that’s unbelievably destructive and irrational.”

Holliday will meet with other developers and the mayor this week. He said has decided to rebuild his San Pablo Street apartment complex for the second time.

Anderson Construction, the owners of the Valdez Street location, tell us they will rebuild as well.