The fire started around 5 p.m. Tuesday and was under control by around 4 a.m. Wednesday.
Air district officials are trying to determine what was burning during those 11 hours. Metal, plastic and fuel at the plant most likely ignited in the fire, according to Gioia.
"I'm sure there will be an investigation that will lead to violation notices," Gioia said in an interview Wednesday morning.
The cause of the blaze is also under investigation. Richmond fire officials are spending the day interviewing workers and combing through burned debris, according to the city's fire chief, Adrian Sheppard.
Several Contra Costa County Community Warning System (CWS) alerts were issued in the hours after the fire began, urging residents to stay indoors.
Over an hour after the blaze started, Richmond Mayor Tom Butt received a county alert on his phone. Butt, a critic of the county's warning system, said that amount of time was too long.
"It's a joke. It's never worked. It did not work yesterday. I'm just very unhappy about this whole thing," Butt said, also in an interview.
When Butt returned to his home later in the evening, it was hard to breathe.
"The whole area of southwest Richmond, including Point Richmond, was just in a toxic fog. There was limited visibility. It was so thick," Butt said.
"The air was so bad, where I live, you literally couldn't take a breath. It was the worst I've ever seen. It was worse than the Chevron fire of 2012," Butt said.
During the major fire at the Chevron refinery in Richmond more than five years ago, thousands of residents went to local hospitals complaining of breathing problems.
This time around there were no reports of similar health complaints, and there were no injuries to workers, said Rodby, the Sims spokeswoman.
But the wind patterns changed -- sending the smoke into different residential neighborhoods. Smoke initially shot up into the air, creating a plume that trailed off in an eastward direction, according to Butt. The wind then shifted and stayed low to the ground.
Those changes led Richmond fire and county officials to expand their shelter-in-place orders.
The initial alert went out at 6:10 p.m., advising people on Wright Avenue to Ohio Avenue in the Nystrom Village area of the city to go inside and stay indoors.
Thirty-five minutes later the alert was extended to include the Santa Fe, Iron Triangle, Atchison Village and North Richmond neighborhoods.
At around 8 p.m. the order was extended to Point Richmond.
Less than an hour after that, the order was expanded yet again to an area between Garrard Boulevard, Ohio Avenue and W. Cutting Boulevard.
The computer-generated audio recordings that explained the new orders were difficult to interpret at times.
"I found some of the alerts to be hard to understand. I don't think they were necessarily clear," Gioia said.
The orders stayed in place until just before 4 a.m. Wednesday, when an all-clear was issued.
As the smoke spread through the city and the shelter-in-place orders expanded, residents expressed criticism and confusion on social media forums like Nextdoor.
"The fire started around 6, some are just now getting alerts, that's way too long a delay," posted Kent Langston at 7:42 p.m.
The Contra Costa County Sheriff's Office, which runs the alert system, released a statement late Wednesday, defending the program's work and disputed claims it was slow to act.
"The CWS worked as designed," said Assistant Sheriff Mark Williams.
"Mayor Butt's statement that it took an hour to get out the first alert after receiving the necessary information from Richmond Fire is totally inaccurate, misleading, and presumptuous," said Acting Sheriff Mark Williams.
The sheriff's department statement said to get out developing information, it used phone, text and email alerts, posted on social media and websites and developed a comprehensive map that included the affected areas.
But, it noted that the fire department did not request to use the warning system's sirens.
The county's hazardous materials program helped determine where the shelter-in-place orders should be expanded, according to the agency's chief environmental health and hazardous materials officer, Randy Sawyer.
"When they started putting the fire out, it cooled down, so the smoke stayed closer to the ground and it moved around. So we added different areas for the shelter-in-place as the evening went on," Sawyer said.
Meantime, Sims says it will investigate the cause of the fire and look to make improvements to reduce the risk of blazes at the facility in the future.
"We apologize for any inconvenience caused to the community by this incident and will continue to be committed to being a good corporate neighbor," a statement released Wednesday afternoon by the company reads.