It could be three more weeks before residents of a southern Colorado town can drink water straight from the tap after dozens of cases of salmonella poisoning were linked to municipal water, putting seven people in the hospital. An analysis indicates the municipal water system in Alamosa is the source of the bacterial outbreak, as suspected, said Ned Calonge, chief medical officer for the state health department. Gov. Bill Ritter declared an emergency Friday in Alamosa County, activating the National Guard and providing as much as $300,000 for response efforts.

The city and county have also declared emergencies as officials scrambled to provide safe water and disinfect the system with chlorine.

The earliest the city water system could be flushed is Tuesday, and disinfecting it and making sure it is safe could take many days, said James Martin, executive director of the state health department. Water agencies from Denver, Aurora and Fort Collins were helping.

As of Friday, 138 cases of salmonella linked to the outbreak had been reported in people from infancy to age 89, of which 47 were confirmed by lab testing, Calonge said. The conditions of those hospitalized weren't released.

Alamosa, with about 8,500 residents, gets its water from a deep well system. The water is pure from the aquifer and is not chlorinated.

Investigators are seeking how the system was contaminated. Possibilities include a compromise in a storage tank or cross-contamination with a sewage line, Calonge said.

About 45 businesses are providing enough bottled water to supply residents for several days, in some cases for free, said Hans Kallam, director of the state Division of Emergency Management. Bulk water is also available from East Alamosa, which is not connected to the city system.

Boiling tap water will kill bacteria, but health officials warned that no one should use even boiled tap water once the flushing of the water system begins. People were warned not to give pets tap water, either.

San Luis Valley Regional Medical Center bought in bottled water, and equipment was being sanitized with alcohol, said Chief Operating Officer Henry Garvin.

"It's becoming much more costly to deliver care, but for patient care it's not going to be an issue," Garvin said, who did not have an estimate on the extra costs.

The city had been working to switch to a chlorinated system, but the outbreak is speeding up the timetable, Calonge said.

Only 15 salmonella outbreaks from public water systems were reported from 1971 to 2004, the federal Centers for Disease Control and Prevention said.

Symptoms include diarrhea, fever and stomach cramps that usually go away within a week, although same cases may require hospitalization.