The county has not established whether the illnesses are connected to the water supply or to one another. Global Water, Maricopa’s main water provider, said the advisory was lifted after follow-up tests came back negative.

The health department is contacting people who tested positive to learn where they had been and what they ate or drank during the five days before becoming ill. That information can help investigators look for a shared source, including possible contamination in food or water.

“Symptoms associated with E. coli” are needed for a hospital to test patients, said Merissa Mendoza, the county’s public health director. Common symptoms include nausea, vomiting, diarrhea and other gastrointestinal problems, she said. Laboratories notify the health department when results are positive, allowing officials to investigate and try to prevent further illness.

Global Water issued its advisory amid concern about possible E. coli contamination, then withdrew it a day later after negative tests. At the time, company representative Joanne Ellsworth said the initial result could have been a false positive and that the company would conduct further assessments. The company had no update on the investigation when contacted about the seven cases.

Officials said it could take several days to determine whether the cases are connected to the water. Until then, the cause of the illnesses remains undetermined.