OAKLAND — Rising up from the charred wreckage of what had been a sleek residential development nearing completion, a sign still stands: “Now selling … New solar, all-electric townhomes.” Behind it, blackened walls sag above piles of twisted, burned rubble.

After a massive fire gutted the Ice House townhome project in West Oakland on Tuesday — the latest in a series of suspicious blazes targeting residential construction projects — developers and housing experts say the fallout could ultimately hit the pockets of Oaklanders already struggling to rent or own homes in the city.

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The fires have delayed the construction of hundreds of homes that advocates say are needed to help address the city’s housing shortage, and builders are tripling or quadrupling their security spending to protect against arsonists, bracing for higher insurance costs and considering switching to more expensive fire-resistant building materials.

“The truth of the matter is, that’s just going to jack up the price of housing,” said Greg McConnell, president and CEO of the Jobs and Housing Coalition, which represents developers and other major employers in Oakland.

Oakland is in the midst of a major building boom that’s changing the face of the city as it brings scores of large developments to house the hordes of people clamoring to move in. Officials permitted 4,284 residential units last year, up from just 274 in 2012. But over the past two years, five fires have targeted four residential construction projects in Oakland and Emeryville, impacting more than 550 housing units in the pipeline. One of those, a 105-unit building on the Oakland-Emeryville border burned once, was rebuilt, and then burned again. A sixth blaze destroyed a luxury apartment complex under construction in Concord last spring.

Officials say four of the prior fires were arson, and the cause of two, including the most recent, remain undetermined. There was no word late last week on the cause of the Tuesday fire at the nearly completed Ice House, a 126 townhome project.

So far, there have been no arrests, despite rewards offering hundreds of thousands of dollars and grainy surveillance footage of a suspected arsonist at the scene of a fire, dressed in black and riding a bicycle.

“Anybody in the development and building business in this area is concerned about it,” said John Protopappas, president and CEO of developer Madison Park Financial Corporation. “If you’re in this business and you’re building with wood, you are thinking about this at all times.”

One of his company’s buildings, which was already occupied, suffered more than $2.5 million in damage when flames engulfed a neighboring construction site on the Oakland-Emeryville border in 2016. Then, on the same day as the Ice House fire, a blaze started in a 124-unit apartment complex Madison Park is building on Hollis Street in Oakland. A security guard put out the flames before they could damage the building.

Madison Park spends $50,000 a month on security at the Hollis Street project, fortifying the construction site with a team of four security guards and a slew of cameras.

SRM Development spent about $400,000 on round-the-clock security and extra fencing to protect its 130-unit apartment building on Broadway during construction, said principal Ryan Leong. The project was finished in August without incident.

Madison Park has started designing new projects with more expensive steel frames instead of the flammable wood frames typically used, and Protopappas expects other developers will follow suit. He estimates the metal framing will cost between $750,000 and $1 million more for a 50,000 square foot building.

And Protopappas is bracing for a possible spike in insurance costs as insurers deem the Oakland area an increasingly risky place to build. Protopappas says his agent already has warned his latest project will see a significant price increase.

Experts say the projects damaged by fire almost certainly will be rebuilt, but the delays could be costly. Interest rates are rising, which means the longer a project takes, the more expensive it becomes, said Eric Tao, managing executive principal of developer AGI.

Rumors are swirling about a possible serial arsonist, with some speculating the culprit is using the fires to make a stand against gentrification. In the West Oakland neighborhood where Tuesday’s fire ignited, residents walk past homeless camps to get to trendy new bars, restaurants, coffee shops and loft apartments. Some long-time residents are upset by the changes. Graffiti proclaiming “(expletive) gentrifiers” defaced a street sign on 27th Street recently, and a church on West Grand Avenue sometimes flashes “stop gentrification” across its electronic sign board.

“Are people upset about the housing crisis? Yes,” said Vanessa Riles, interfaith and community organizer for East Bay Housing Organizations. “Are people upset that market rate development seems to be a priority and affordable development is not? Yes … People are upset about that and rightfully so.”

Neither the Hollis Street project nor the Ice House project included any units reserved for low-income families.

Ernest Brown, co-executive of pro-development advocacy group East Bay for Everyone, was considering buying one of the Ice House townhomes. Brown, a 27-year-old business analyst who moved to Oakland three years ago from Atlanta, splits $4,400 a month in rent with three roommates. The price goes up each year, and Brown, tired of renting, had been exploring whether he could afford to buy a home with several other people.

But Brown was sensitive to his status as an Oakland gentrifier. He gravitated toward new construction because he didn’t want to buy a building where tenants had been or would be displaced.

“The Ice House-type development provides a way out of that,” he said. “Here’s my way to put down roots in Oakland without disrupting someone else’s roots.”

Now he’s back to square one.

“Now that that option has gone up in flames, I’m now stuck with renting for the foreseeable future,” he said. “So that’s kind of unfortunate.”