Sixteen Coloradans have been sickened in a national salmonella outbreak, including six whose illnesses have been traced to Vitamin Cottage peanut butter, according to the state health department.

The Lakewood-based natural foods company voluntarily recalled its packed, fresh-ground peanut butter as a precaution earlier this month.

At the time, Vitamin Cottage said the Colorado Department of Public Health and Environment had determined three people who ate the product had the same strain of salmonella involved in the Peanut Corp. of America recall.

That number has since grown to six, Mark Salley, communications director for the health department, said Sunday.

The salmonella outbreak has sickened some 600 people in 43 states and is being linked to nine deaths.

More than 1,900 products have been recalled and Peanut Corp. of America is under FBI investigation. The company filed for bankruptcy Friday.

Leading brands of jarred peanut butter are not affected.

Alicia Cronquist, epidemiologist at the Department of Public Health and Environment, said Colorado authorities first thought a Georgia plant was the source of the Vitamin Cottage sicknesses.

When a boy with a tree nut allergy became sick, they discovered the tainted product came from a Peanut Corp. of America plant in Texas that authorities said had operated since 2005 without an inspection.

"His parents were very careful about what kind of nuts he ate," Cronquist said.

The Colorado victims range in age from 2 to 60. One person had to hospitalized.

burnetts@RockyMountainNews.com or 303-954-5343 The Associated Press contributed to this report.