ALAMOSA, Colo. - Officials said Monday they have ruled out wastewater contamination, disgruntled workers and terrorism as sources of salmonella bacteria in drinking water that have sickened more than 200 people.

A plan to disinfect the municipal water system will begin Tuesday as crews start running chlorine through it, Lisa Stigall, a spokeswoman with the state emergency response team, said Monday.

The roughly 8,500 residents of the southern Colorado town won't be able to drink the water until the chemical is washed out. That could take three weeks.

The number of cases was 217, with 68 confirmed through lab tests, said state health department spokeswoman Lori Maldonado. Nine people have required hospital treatment, and one remains in the hospital.

Test results Monday confirmed earlier findings of salmonella in the city's tap water.

The aquifer that's the town's water source appeared to be fine, Stigall said.

"There are many unknowns," Stigall said. "Many questions will be answered as they move through this process."

The first salmonella victim began showing symptoms around March 8, and state health officials became aware of the outbreak a week later, said Ned Calonge, the health department's chief medical officer.

Alamosa residents were told March 19 that they should not drink the water but that they could bathe in it if they didn't ingest it. Neighboring communities, businesses and the Colorado National Guard have trucked in bottled water and tankers.

The bacteria are typically spread by food. Salmonella can cause diarrhea, fever and stomach pain. Victims generally recover on their own, but the elderly, infants and people with impaired immune systems may require treatment.

Alamosa is about 160 miles south of Denver.