"We are not going to open Rennaissance 1 tonight," Contra Costa Fire spokesperson Steve Hill said at a press briefing just before 5 p.m.
The announcement meant some 250 residents would not be allowed to return to their apartments Tuesday night, across the street from the smoldering ruins of a $55 million construction project.
RELATED: Neighboring apartments evacuated during massive Concord fire
"We still have some problems there that we need to knock down, some walls that are unstable," Hill said.
After some residents fled with only their pajamas and their pets, the Red Cross hosted only four people in its shelter Wednesday night, saying most had found other places to stay -- but continued bracing for a crowd at dinnertime on Thursday.
Two days after it started, the fire that gutted a Concord apartment complex under construction is still smoldering. Crews are demolishing parts of the building to get to the hot spots underneath. pic.twitter.com/Og3tT5tuFg— Jonathan Bloom (@BloomTV) April 26, 2018
"We're all kind of on the same pins and needles as everyone else, waiting for word form the fire department," said Diane Dupuy, the organization's Contra Costa County disaster chair.
The fire department said it's made good progress, tearing down entire stories of the charred buildings with a tool called a Spudnik.
"It's basically just a big old iron beam, and it is kind of like taking a baseball bat to a wall," one firefighter explained to us.
RELATED: Could fire at Concord building under construction be arson?
Fire crews demolished enough to let arson investigators from the Bureau of Alcohol, Tobacco and Firearms enter the site and begin searching for clues. The demolition also gives the fire department access to stubborn hotspots still burning beneath the debris.
About 250 people remain evacuated from a building next to the Concord apartment complex fire. The wall at the right side of this picture is still in danger of falling onto their homes. pic.twitter.com/U28Ss75M7B— Jonathan Bloom (@BloomTV) April 26, 2018
"There's been a few flare-ups," said Hill. "You can certainly see some smoke from a few of the hot spots that are out there."
Even with the worst dangers taken care of, another problem still residents from returning home Thursday night: although their apartments were spared by the flames, they were filled with smoke.
"We know right now that the air quality is not healthy," Hill said.
Property managers planned to bring in a cleanup company in hopes of having the smoke cleared by late morning on Friday. Beyond the smoke hazard, eight apartments remain red tagged, near where scaffolding fell across the street as the fire burned.
Live video: Concord fire update — Arson investigation and evacuation orders. https://t.co/TikdCETFe5— Jonathan Bloom (@BloomTV) April 26, 2018
"They're red tagged because right now, there's s still a threat to them from any potential collapse form that corner, the far corner," Hill said.
The Rennaissance Two complex was 60 percent complete, slated for move-ins in September. Investigators aren't saying much about similarities to the apartment construction fires last year in the East Bay, but Hill said they are gathering evidence.
"There were a couple of security cameras in there, and our investigators did carry them off," he said.