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DENVER — The Colorado Department of Public Health and Environment, the Centers for Disease Control and the Food and Drug Administration are all investigating an E. coli outbreak in the Denver metropolitan area, FOX31 Denver first reported.

In the second week of October three Jimmy John’s restaurants in the Denver Metro area reportedly served up sandwiches that sickened eight people with E. coli bacteria.

Friday, more people contacted FOX31 Denver to say they became ill after eating at Jimmy John’s recently. They came forward after hearing about the investigation on FOX31 Denver news.

LINK: E. coli symptoms and resources

“We believe that their illness came from a produce item that was on those sandwiches that they ate,” said Alicia Cronquit, epidemiologist with the Colorado Department of Public Health and Environment.

Cronquist said customers ate the bad food between Oct. 5 and 9.  They got sick between the 7th and 15th.  The health department was notified about all eight cases Oct. 18 and 22.

The Department of Public Health has not closed down the three restaurants, and will not identify their locations because Cronquist said they do not believe the restaurants are at fault.

An official stood by that decision Friday. The number of confirmed cases remained at eight.

“Our leading hypothesis for what’s happened is that there was a contaminated produce item that was distributed to the stores,” Cronquist said. “We have not identified any food handling issues at the particular establishments that we think would contribute to illness.”

A local teenager is among those still hospitalized from the E. coli in Denver.

Family friends reached out to FOX31 Denver looking for answers as to why the public had not been notified. We took that question to state health officials and they told us it’s because the tainted food no longer appears to be a threat.

“If we were to see additional cases that were potentially part of this outbreak, I think we would take different action,” Cronquist said.

The CDC confirms that no other strains of the E. coli bacteria have been reported in surrounding areas or states.

The health department is now waiting on an investigation by the FDA tracing what produce might be to blame. The FDA won’t comment on open investigations, but Cronquist said it is extensive.

“They look at a lot of receipts and invoices and try to take it all the way back to the source to see which one of the food items came from the same source at all three restaurants,” she said.

State officials say that investigation is key to moving forward.

“We’re happy to notify the public when we know… when we know what the food item was for sure,” Cronquist said.

According to the Colorado Department of Public Health, the local Jimmy John’s restaurants and corporate representatives are concerned and have cooperated throughout the investigation.

When contacted by FOX31, a Jimmy John’s corporate representative declined to comment on the outbreak.