Calling it a "very important break in the case," the Food and Drug Administration today said it had found the strain of Salmonella responsible for a nationwide food-poisoning outbreak (Salmonella Saintpaul) in a Mexican-grown jalapeño in a Texas plant. The finding prompted a new warning for consumers to avoid eating fresh jalapeños or items made with them (fresh salsa). Processed or pickled peppers are still safe to eat.

The discovery is the first time the strain of Salmonella Saintpaul has been linked to a piece of produce in the months-long investigation that began with a probe of tomatoes in April. The agency issued a warning to avoid certain kinds of tomatoes in early June but lifted it last week.

Since April, 1251 persons infected with Salmonella Saintpaul with the same genetic fingerprint have been identified in 43 states, the District of Columbia, and Canada.Two deaths have been attributed to the outbreak.

The finding doesn't mean that Mexican jalapeños are the source—the pepper may not have been contaminated on the farm but somewhere else in the distribution chain. On the conference call announcing the discovery, the FDA identified the vegetable distribution plant as Agricola Zaragoza, Inc. of McAllen, TX.  It’s a small operation, so it’s unlikely that this is the major source for all the problems. The peppers processed at the plant are being recalled.

The Centers for Disease Control and Prevention said that in addition to peppers, tomatillos are packed at this plant. Officials didn’t say where in the distribution chain this packing plant falls. Is it one step away from the field or many?

Still, it's a solid piece of evidence in an investigation that has confounded researchers—and consumers— for many months.