The source of E. coli cases in Hyrum remains unknown more than a month after the bacteria was discovered, reports the Associated Press.

"Our investigation is still under way," Bear River Health Department spokesman Mike Weibel said. "We have not ruled anything out, and Health Department tests of Hyrum’s water show that it is safe to drink."

Residents have speculated that the bacteria could have originated in the culinary water, since a new water line was recently installed in the High Valley subdivision, but city officials maintain that proper precautions were taken.

The Utah Department of Environmental Quality is assisting the local health department in the investigation.