U.S. health officials are still struggling to find the source of the salmonella outbreak in certain types of tomatoes that as of July 4th has sickened 922 people in 40 states since mid-April. The FDA and the CDC are turning their sights to produce imported from Mexico according to a CNN report last week. The Food and Drug Administration (FDA) alerted growers and brokers handling their products that, starting on Monday July 7, inspectors will stop shipments from Mexico of ingredients common to Mexican cuisine, CNN reported. Tomatoes continue to be the primary focus of the investigation but officials have expanded it to include produce commonly eaten with tomatoes. Cilantro, jalapeno peppers, serrano peppers, scallions and bulb onions are among the products to be further scrutinized. The U.S. Centers for Disease Control and Prevention says Salmonella Saintpaul, the strain involved in the outbreak, is rare. Typically, the CDC sees only about 400 cases of Saintpaul infections in humans each year. Salmonella can cause fever, diarrhea, nausea, vomiting and abdominal pain, according to the FDA.