Carbon dioxide is believed to be the culprit at Ghiringhelli Specialty Foods. There were 71 people that were transported to the hospital; the first 10-15 were the most serious. Most were complaining of nausea, dizziness and breathing problems.
In the afternoon, many of the people who were transported to the hospital later returned to Ghiringhelli Specialty Foods.
They've been told not to talk to the media, but one woman said she was having lunch when she suddenly noticed she has having difficulty breathing. Then she noticed another woman throw up and that's when she started getting concerned.
Fire crews say they were called for a possible carbon dioxide leak and shut off the carbon dioxide system to alleviate the problem. They say some people were vomiting, others were nearly unconscious and some were light-headed. When they arrived they quickly set up a field triage.
At first the owner of Ghiringhelli Specialty Foods raised some questions about the emergency. He thought the whole incident may have been more of a mass anxiety episode, than a mechanical problem.
"Ten minutes ago they told me we were clear to go back in that building, so there's absolutely, I think this, personally I think it's a false alarm because the air was fine," Mike Ghiringhelli said.
The site manager said the problem came from the company's cooling systems, so that system was quickly shut down. Later on Friday, the owner said the company will investigate what happened.
"Well, we don't have 70 some odd people complaining of something, without something happening in there, so we did some levels in there, so that will be followed up with the investigation," Vallejo Fire Department spokesperson Patrick Dunn said.
"No, I didn't feel any symptoms, but I've seen a whole bunch of other people, they said they were feeling fine, then one minute they said one minute they couldn't breathe, then they were falling, fainting," worker Justin Breeden said.
Most of the workers initially taken to area hospitals have since returned and some continued working in the afternoon.
Forty-five people were treated at Sutter Solano Medical Center. The hospital set up a triage area in tents in the parking lot with cots and medical equipment where workers were first evaluated. One of them was admitted to the hospital. The hospital spokesperson says that person is in serious condition.
Dr. Laybon Jones says the big danger with carbon dioxide poisoning was the chance that it could lead to cardiac problems and in the worst case cardiac arrest.
Thirty people were taken to Kaiser Permanente Medical Center in Vallejo. All 30 were evaluated there and the hospital says they were all treated and released.
Carbon dioxide is used in food preparation for carbonation, dehydration, and keeping foods cool. Dry ice is carbon dioxide in its solid form.
Local authorities and Cal/OSHA are still investigating exactly why so many people got sick on Friday.
Laura Anthony, Mark Matthews and Sergio Quintana contributed to this story.