WASHINGTON – One part of Mexico – Baja California – has been cleared of suspicion in the outbreak of salmonella-tainted tomatoes, but U.S. officials appear no closer to finding the culprit.

The best lead remains a cluster of nine illnesses listed last week among patrons of an unidentified restaurant. Food and Drug Administration investigators were at work Monday tracing records of the restaurant's various suppliers, part of the painstaking work of cross-checking common suppliers for other parts of the country where people got sick.

The government counts 228 illnesses in 23 states linked to salmonella-tainted tomatoes, and is urging consumers nationwide to avoid raw red plum, red Roma or red round tomatoes unless they were grown in specific states or countries that FDA has cleared of suspicion. Check FDA's Web site – www.fda.gov – for an updated list. Also safe are grape tomatoes, cherry tomatoes and tomatoes sold with the vine still attached.

The FDA has said that central and southern Florida and parts of Mexico were supplying most of the tomatoes sold when the salmonella outbreak began in early April, and thus are leading suspects. But tomatoes from northern Florida are in the clear because they weren't being harvested that long ago, and those tomatoes are arriving in stores now, often with state-issued certificates guaranteeing they weren't implicated.

Likewise, the FDA cleared Baja California over the weekend, because its harvest began April 26 and the earliest known patient in the salmonella outbreak fell sick on April 10, FDA food safety chief Dr. David Acheson said Monday.

Testing of tomatoes, including those from various parts of Mexico, hasn't yet turned up any salmonella, Acheson said.

Mexican Economy Secretary Eduardo Sojo said the Mexican government might seek compensation for the Mexican producers who are losing millions of dollars because they can't export to the U.S.

“What we want is to get at the truth .... If the truth is that our country isn't responsible for making people sick in the U.S., then they need to lift the restriction on Mexican tomatoes,” Sojo said.

He added: “If this isn't resolved soon, the impact on the national industry will be severe.”