Dr. Javier Trujillo, undersecretary for food safety and quality in Mexico's Ministry of Agriculture, said yesterday that the FDA got the names of the four operations from Mexican officials, not from searches that the FDA said it had done to find the source of the contamination.
Mexican authorities had found problems with the farming companies during recent inspections, but none that indicated hepatitis A contamination, according to Trujillo.
The allegation raised questions about FDA's green onion "trace-back" process, which is supposed to track the route produce travels from the field to the table, and revealed tension between the two governments, whose inspectors are now in Mexico together trying to track down the source of hepatitis A.
As of yesterday, the virus had sickened 635 people who ate at the Beaver Valley Mall Chi-Chi's in Center. Investigators believe it came to restaurants here and in Tennessee, Georgia and North Carolina by way of contaminated scallions.
Trujillo said that during a telephone conference call on the morning of Nov. 21, Mexican officials gave FDA officials the names of four onion-exporting companies that had been cited for "deficiencies in agricultural and processing practices" during that month.
The Mexican officials had no means of determining whether onions from one of those four companies ended up in the salsa at Chi-Chi's restaurant in Beaver County or in the other places where hepatitis outbreaks occurred, Trujillo said.
An FDA press release dated the same day, however, implicated the same four Mexican firms, saying they were associated with hepatitis A illnesses in Tennessee, Georgia and Pennsylvania.
The FDA disputes Trujillo's version.
Joe Baca, a food safety official with the FDA, said agency officials gave the names of companies it had identified through trace-backs to Mexican officials on or before Nov. 21. The four companies the FDA has named are Dos M Sales, Agro Industrias Vigor, Tecno Agro Internacional and Agricola La Laguna, which also goes by the name Sunfresh.
"Those four firms were the four firms to which we traced the product," said Baca.
Trace-backs are done by using identifying numbers on manifests and other documents that are required for all shipments of produce coming into the United States from foreign countries.
Every shipment that crosses the border from Mexico to the United States has an alphanumeric identifier, which corresponds to the producer or exporter, said Sam Longanecker, supervisor of agricultural inspectors at the Otay Mesa Cargo Facility near San Diego, where many shipments of Mexican produce cross into the United States.
The manifest also is supposed to include the name of the firm to which the product is being shipped. Those numbers theoretically should follow shipments from point of origin to final destination, and could be used to trace them back to their source.
"It's not any great detective work to trace back the product. You just trace back a paper trail and identify where the product came from," said Baca.
In the case of green onions, the way they are packed and shipped precludes much handling.
The onions are put in open boxes in the field, then typically taken to a nearby packing plant. There they are trimmed, washed and packed in waxed cardboard boxes. A sheet of paper board, very thick paper, is placed on top of the onions, and ice deposited on top of that. Then the box is sealed.
Though some boxes might be opened for inspection, most travel across the border, into a distribution center (often in southern California) and on to distributors or wholesalers in other states without being opened or exposed to potential contaminants other than the ice.
But food industry experts say trace-backs can be complicated by a number of factors, including poor record-keeping and distributors who combine produce from different sources into one shipment.
"The produce industry is a very complex distribution network," said Kathy Means, spokeswoman for the Produce Marketing Association.
In mid-October, FDA started tracing scallions implicated in a Knoxville, Tenn., outbreak, according to Jack Guzewich, director of emergency coordination and response in FDA's Center for Food Safety and Applied Nutrition. In early November, the agency started tracing green onions implicated in a hepatitis A outbreak in Georgia.
"As a precaution, we began a trace-back from Pittsburgh even before the epidemiology implicated green onions," Guzewich said. "Those individual trace-backs, by going back through the various distributors and wholesalers through the system -- eliminating one lot from this, one from that -- we traced them back to these four companies in Mexico."
FDA started tracking scallions implicated in a North Carolina outbreak in November, too, but as of last week that trace-back still wasn't complete.
Trujillo said that the FDA had the names of a number of exporters whose product might have ended up in areas where hepatitis A outbreaks occurred on dates that would correspond with the development of illnesses among those who ate the onions. But he maintains the FDA officials did not have a short list of companies, and were under pressure to take action.
Mexico, fearing that all of its onion producers would be banned from exporting, offered the four names of companies (out of 26 producers) that had violations during recent inspections. Some of the violations were failure to properly document the procedures used in the packing houses. None of the violations, according to Trujillo, could be tied to hepatitis A.
"They needed something, and Mexico offered something," he said. "For the FDA, it's easier to blame another country. Just as it would be easier for me to say a problem was the fault of Guatemala than the fault of Mexico.
"The question for the FDA is, where is the evidence of the trace-back?"
The FDA has told reporters asking that question that it is proprietary information and that they can only give the endpoint of the trace-back, not the intermediate stops.
Trujillo said proprietary information should not prevent health officials from two countries from sharing information during a crucial investigation that involves the health of many people.
"They won't show me. They have shown me nothing."
He says he believes that it will be extremely difficult to find the source, and that while the investigation is under way, officials should not be releasing information.
"This is a matter for scientists. After the trace-backs, after the investigations in the fields, after the scientists study it, after they all finish, then we will take action."
But the inspections so far seem to be indicating that the companies in question are following good agricultural practices, and that their packing plants are complying with health and sanitation requirements.
He said he expected the inspectors to finish by week's end. The FDA, however, said it expected its investigators to be in Mexico for at least two weeks.