(UPDATED COVERAGE, 4:45 p.m.) An E. coli outbreak of unknown origins has sickened up to 23 people in the St. Louis area as of Oct. 28 and has spurred Schnucks Markets Inc. to pull some fresh produce from shelves and salad bars.

Investigators from the Centers for Disease Control are expected to arrive in St. Louis by Oct. 29, according to Missouri state health officials.

County and state health officials say they don’t have any indication of the cause of the illnesses. No fresh produce has been implicated. On Oct. 26 the Missouri Department of Health issued a news release, stating that in the previous 24 hours the St. Louis County Health Department reported 14 cases of foodborne illnesses.

The first illnesses were reported during the weekend of Oct. 22-23. Some people have been admitted to hospitals, but no one has died.

In a preemptive and voluntary move, the food safety team for the Schnucks grocery chain pulled some fresh produce from shelves. Lori Willis, Schnucks communications director, said Oct. 28 the chain took the precautionary move out of its commitment to its customers’ safety. Schnucks has about 65 stores in the St. Louis metro area.

UPDATED: E. coli outbreak hits St. Louis; origin remains unknown“The health department’s news release declaring an E. coli outbreak raised concerns,” Willis said.

“The Schnucks food safety team is certainly taking this very seriously — proactively and voluntarily, pulling and replacing products that recent history tells us could be sources. We were not asked to do this. This was a precaution taken by our food safety team.”

State and county health officials don’t know the scope of the outbreak, but is has spread into four counties and has the potential to continue to cause more illnesses because E. coli has up to a 10-day incubation period.

Cases of E. coli have been reported in the city of St. Louis and the Missouri counties of St. Louis, Jefferson and St. Charles, as well as St. Clair County in Illinois.

According to reports in the St. Louis Post-Dispatch, different Schnucks locations took different precautions. One location pulled strawberries, lettuce and croutons out of its salad bar on Oct. 26. A downtown St. Louis Schnucks had already pulled some fresh-cut lettuce products because of an unrelated recall and posted a sign reassuring customers that its salad bar does not use lettuce involved in the recall.

As of Oct. 28, 16 specimens had been sent to the Missouri State Public Health Laboratory for testing. It takes several days to confirm specific E. coli strains. However, four of the specimens already tested positive for shinga toxin, a byproduct of E. coli.

Health officials said the number of sick people is unusual. For the entire year of 2010, St. Louis County had only five reported cases of E. coli. Doctors and emergency room staffs have been asked to watch for potential cases and be sure to report them so investigators can determine common denominators among the victims.