WASHNINGTON (1010 WINS)  -- Inspectors are collecting soil, water and produce samples, reviewing export logs and combing packing plants in three major tomato-growing states in Mexico.

But the U.S. Food and Drug Administration appears no closer to finding the source of a mysterious salmonella outbreak that has sickened more than 900 people nationwide. It's not even certain that tomatoes are the cause.

And, as the FDA continues looking for the source of the salmonella, it is looking at jalapeno peppers and salsa ingredients, such as cilantro and Serrano peppers.

Investigators with the Centers for Disease Control and Prevention have interviewed people sickened in June to find out what they ate and to compare their diets with those of healthy relatives and neighbors.

Officials have not revealed early findings, except to say they supported the investigation's new move.

Among the possibilities FDA has said it was exploring is whether tomatoes and other produce are sharing a common packing or shipping site where both might become contaminated, or whether multiple foods might be tainted while being grown on adjoining farms or with common water sources.

Officials have said some patients have told the CDC they ate raw tomatoes in fresh salsa and guacamole.

As of Friday, 943 people infected with salmonella with the same genetic fingerprint have been identified in 40 states, the District of Columbia, and Canada, according to CDC. The illnesses are thought to have begun in early April. There have been 225 cases reported since June 1 - evidence that the source likely has not been contained.

So far, Texas is by far the leader in reported illnesses, with 356 reports of ill people as of late Friday. New Mexico has 98 reported illnesses, while Illinois has 93.

CNN reported that the U.S. investigation is focusing on imports from Mexico, and that starting Monday inspectors will stop shipments of produce for common Mexican cuisine ingredients.

In Mexico, a team of three FDA inspectors has gone through five farms in the western states of Jalisco and Sinaloa in the past two weeks, looking at all aspects of tomato production: the greenhouses where they are grown, the packing plants where they are shut into boxes, the shipping methods for the trip north to the United States.

They also plan to visit the northern state of Coahuila to finish up their study.

The results can't come too soon for the three Mexican states that were targeted by the FDA, along with farms in Texas and Florida.

The U.S. tomato industry has taken a $100 million hit as restaurants temporarily dropped tomatoes from their menus, and farmers have had to plow under their fields or leave crops to rot in packinghouses.

Salmonella can be transmitted to humans when fecal material from animals or humans contaminates food. Fever, diarrhea and abdominal cramps typically start eight to 48 hours after infection and can last a week. Many people recover without treatment. But severe infection and death are possible. At least 130 people have been hospitalized in this outbreak, the CDC says.