MEXICO CITY — Export-quality tomatoes labeled "Ready to Eat" in English flooded Mexico City markets on Thursday after a salmonella scare in the U.S. stopped them from crossing the border.

There is no proof that Mexico provided the contaminated tomatoes that caused the alarm. The U.S. Food and Drug Administration is still hunting for the source of the outbreak that has sickened at least 167 people in 17 U.S. states since mid-April.

The FDA has cleared imports from at least six countries — but not Mexico, which sends 80 percent of its tomato exports to the United States. Florida tomatoes are also under suspicion.

But some U.S. consumers already associate the outbreak with Mexican produce, and exports from Baja California came to a halt this week.

Jesus Macias, the sales manager at the Productora Agricola Industrial del Noreste, normally ships 50,000 boxes a day to an importer in Chula Vista, California. Since the scare, "we can't sell a single box of tomatoes," he said.

Instead, he is shipping his top quality tomatoes to Mexican markets, and letting rot the lesser-quality produce normally sold to Mexicans.

At Mexico City's bustling central supply market, where food arrives from across Mexico to supply 20 million people who live in and around the capital, truckloads of tomatoes are arriving in boxes originally meant for the U.S.

"Sweet treat. Premium quality," says lettering in English, advertising lost on Mexico's Spanish speakers.

Most consumers do not even know about the U.S. salmonella scare. And those who do, rarely care. Mexicans are accustomed to washing all produce because the vegetables sold on the national market are not held to the same standards as those certified for export.

Sergio Martinez, a 40-year-old bricklayer buying 4.5 pounds (2 kilograms) of tomatoes, says he isn't worried about a little salmonella. He washes all of his produce with bleach and water.

"What the U.S. doesn't want is what we see here. They always send the best stuff over there, from avocados to tequila," he said. "What ends up here is second-rate. Almost all vegetables are contaminated with something because they water them with sewer water and put on a lot of chemicals."

Mexican consumers are benefiting from the scare. In the capital's vegetable markets, consumers can now buy top quality tomatoes for 8 pesos per kilogram (35 U.S. cents a pound). That's a third less than normal prices.

Mexican officials insist there's nothing to worry about here.

"The Mexican tomato is safer and cleaner than ever," Agriculture Secretary Alberto Cardenas told Televisa network Thursday.

Even U.S. officials agree that certified Mexican exporters are among the safest in the world. Their fields are irrigated with fresh water, and their packing plants are staffed by workers covered head-to-toe in sterile clothing. Inspectors monitor the process at every step.

Ricardo Montiel, 41, manning a stand with mounds of tomatoes, apples and avocados, said it was unfair to single out Mexico without proof.

"The gringos are really demanding about quality," he said. "But the problem didn't originate here. It is as easy as looking around and seeing that people haven't gotten sick."