AUTLAN, Mexico — 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.

The FDA is not even 100 percent sure that tomatoes are the cause — adding peppers and cilantro Saturday to its list of foods under investigation in the outbreak.

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 U.S.

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.

Bonanza 2001 farm in Autlan, Jalisco, which normally exports about 12,000 tons of tomatoes a year to the U.S., has hundreds of tons sitting in a warehouse near the Texas-Mexico border as demand has plummeted, said spokesman Luis Almejo.

They may rot.

Sinaloa growers also face big losses.

“We’re demanding that they release those results as soon as possible so that Sinaloa can be cleared of any suspicion,” said Manuel Tarriba, president of Sinaloa’s Tomato Growers Association, adding that he expects some results by the end of next week.

The outbreak, which began in April, has affected 943 people so far in 40 U.S. states, more of a third of them in Texas, according to the Centers for Disease Control and Prevention. There have been 225 cases reported since June 1 — evidence that the source likely has not been contained.

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.

Mexico has not calculated its losses. But growers here worry they still may be under a shadow of suspicion as late as November, when greenhouses harvest their summer tomatoes.

FDA spokesman Kimberly Rawlings said Saturday evening that the FDA “is looking into tomatoes, cilantro, jalapeno peppers and Serrano peppers. We have started testing on those items within the past few days.”