But now officials are looking at common ingredients used to make salsa.
Jalapeño peppers are also one of the foods now suspected.
The government interviewed dozens of victims and many of them had eaten fresh salsa before getting sick.
Experts fear hundreds more will become ill before the FDA can track down the source.
"We have to get better at identifying outbreaks sooner, preventing them in the first place and then if a problem does occur we have to get better at responding more quickly," said Amy Philpott, United Fresh Produce Association.
The FDA is also checking into cilantro and serrano peppers.
The outbreak affected 940 people.