An ongoing E. coli O157:H7 in Arizona that has been linked to a local Mexican restaurant chain has potentially doubled in size to 33 cases with 15 hospitalizations being investigated, according to the Maricopa County Health Department.

After initially reporting 15 cases, the health department on Tuesday issued an update saying that it had interviewed 33 individuals had reported bloody diarrhea and  and had eaten at Federico’s Mexican Restaurant in Litchfield Park. Of those cases, 15, including children have been or are still hospitalized. At least two have developed hemolytic uremic syndrome (HUS), a very serious complication, health officials said.

As Food Safety News reported, preliminary test results are showing that the patients contracted E. coli O157 infections. The health department has visited the restaurant to collect food samples.

Only one Federico’s location, 13132 W. Camelback in Litchfield Park, has been tied to the the outbreak.

“The restaurant has been extremely cooperative with our investigation. In fact, out of an abundance of caution and concern for their customers, the restaurant is voluntarily closing,” said Steven Goode, deputy director of MCESD, last week.

“Anyone who has eaten at this particular Federico’s Mexican Food from on or after July 23 AND is experiencing bloody diarrhea should see a healthcare provider so a stool culture can be ordered,” read the Aug. 6 update. “It is important for health care providers to be aware of this outbreak because treating children with antibiotics for these bacteria can increase the risk of serious consequences.”

The health department is advising doctors who have patients who they suspect may be related to the outbreak to order a stool culture and contact MCDPH’s disease reporting line at 602-747-7500.

This story has been updated with the Maricopa County Health Department’s Aug. 6 update.