The Colorado Department of Public Health and Environment has warned all residents in Alamosa to stop drinking and cooking with tap water because they said it might be linked to a salmonella outbreak.

Alamosa, a city of 8,500 people about 160 miles south of Denver has reported 33 cases of salmonella, while other 46 cases are still being investigated, the Denver Post wrote. No results on tested tap water have confirmed the presence of salmonella though.

Salmonella is a common bacterium that can cause serious and sometimes fatal infections in young children, frail in elderly people and others with weakened immune systems. Symptoms of salmonella include fever, diarrhea, nausea, vomiting and abdominal pain. Most people recover from salmonella illness without special treatment, but cases of severe diarrhea require medical attention and there’s a risk of infection spreading from the intestines to the bloodstream, a condition that could turn fatal.

First cases of salmonella infection began to appear about a week ago, mainly in people younger than 18, Alamosa County Public Health representative Connie Ricci said.

Boiling water for 15 seconds will kill bacteria, but health officials urged residents to use bottled water for brushing teeth, washing dishes, making ice, cooking, drinking and making baby formula. The tap water is still good for bathing, as long as people are careful not to ingest it.

According to Dr. Ned Calonge, chief medical officer for the Colorado Department of Public Health and Environment, more than 30 companies have offered to donate bottled water to the community.

Health officials are still working to find out how the water was contaminated. However, the water system will be flushed in the next few days, a process that could take a week or more. Until the process is complete, residents are urged not to consume any municipal water, even if it is boiled, city officials announced.

A similar case of salmonella contamination in a deep-well water supply occurred in Riverside, Calif., in 1965. About 16,000 people were stricken.