The Centers for Disease Control and Prevention announced an investigation Wednesday into an E. coli outbreak that's sickened 17 people in eight states.

The source of the outbreak has not been determined, but seven people in Maryland reported eating a pre-made chicken caesar salad before getting sick. The salads were purchased at various Sam's Clubs, according to the Maryland Department of Health.

The salad, called Ready Pac Foods Bistro Chicken Raised Without Antibiotics Caesar Salad, was sold only at Sam's Club, according to a statement from Bonduelle Fresh Americas, the company that makes the salads.

Investigators are looking into whether the E. coli found in the salad is genetically similar to the E. coli making people sick, which would indicate that the salad is a source. Patients in the seven other states affected by the outbreak — Arizona, California, Colorado, Idaho, Montana, Washington and Wisconsin — did not initially report eating this salad.

No deaths have been reported, but seven people have been hospitalized. Two developed a condition called hemolytic uremic syndrome, which is a type of kidney failure.

The CDC says that people should not eat or sell the pre-made salads with a "best by" date of Oct. 31, 2019. If you have this salad in your home, throw it away.

CORRECTION (Nov. 21, 2019, 10:21 a.m. ET): An earlier version of this article misstated the name of the salad linked to the outbreak. It is the Ready Pac Foods Bistro Chicken Raised Without Antibiotics Caesar Salad, not the Ready Pac Bistro Bowl Chicken Caesar Salad.

Follow NBC HEALTH on Twitter & Facebook.