Health officials in northern Nevada are investigating more than a dozen confirmed and probable cases of E. coli that might be associated with a Reno restaurant.

Washoe County Health District spokesman Phil Ulibarri says 18 of the 21 cases seem to be related to Twisted Fork Restaurant in south Reno. The restaurant’s general manager says it will remain voluntarily closed until an investigation is complete.

Authorities say health officials are working with Twisted Fork to determine the source and investigating food products, storage and preparation methods. The Health District says the restaurant is fully cooperating with the investigation.

Ulibarri says the health district was originally notified of eight E. coli cases on November 4.

Officials say these cases are not related to Chipotle restaurants or cases in el Dorado County.