WASHINGTON (AP) — An outbreak of stomach illnesses in Iowa and Nebraska has been linked to salad mix served at local Olive Garden and Red Lobster restaurants and supplied by a Mexican farm.

The outbreak of cyclospora infections has sickened more than 400 people in 16 states. The Food and Drug Administration says it is still working to determine whether the salad mix is the source of illnesses in the other 14 states.

"It is not yet clear whether the cases reported from other states are all part of the same outbreak," the agency said in a statement. "The investigation of increased cases of cyclosporiasis in other states continues."

Both Olive Garden and Red Lobster are owned by Orlando-based Darden Restaurants. In a statement, Darden spokesman Mike Bernstein said the FDA’s announcement is "new information."

"Nothing we have seen prior to this announcement gave us any reason to be concerned about the products we’ve received from this supplier," Bernstein said.

The FDA said it traced illnesses from the restaurants in Nebraska and Iowa to Taylor Farms de Mexico, the Mexican branch of Salinas, Calif.-based Taylor Farms. The company, which provides produce to the food service industry, said its facility located about 180 miles north of Mexico City in San Miguel de Allende is the only one of its 12 sites to be connected to the cases.

In an email, the chairman and CEO of Taylor Farms, Bruce Taylor, said the Mexican plant produced 48 million servings of salads for thousands of restaurants in the Midwest and eastern U.S. in June, the month the outbreak started. He said the facility has an extensive water testing program.

"All our tests have been negative and we have no evidence of cyclospora in our product," Taylor said. "We are working closely with the FDA to continue this investigation."

Taylor said Taylor Farms de Mexico does not supply Olive Garden and Red Lobster restaurants in Texas, the state with the second most illnesses in the outbreak. According to CDC, 113 of the illnesses reported so far were in Texas. Iowa has had 146 illnesses and Nebraska 81.

In an additional statement on the company’s website, Taylor Farms says the Mexican facility is "state of the art and has an exceptional food safety record." The statement said the product is out of the food supply.

The FDA said it had audited the Mexican processing facility in 2011 and found "no notable issues," according to the agency. The agency said it would increase surveillance efforts for green leafy products imported from Mexico.

The most recent known illness in the two states linked to the infected salad was in Nebraska a month ago. The typical shelf life for a salad mix is up to 14 days.

There have been more recent illnesses in other states. According to the Centers for Disease Control and Prevention, the most recent illness was July 23 but centers did not specify a location.

The agency said its investigation has not implicated any packaged salad sold in grocery stores.

——

Follow Mary Clare Jalonick on Twitter at http://twitter.com/mcjalonick