(CNN) – The outbreak of E. coli linked to romaine lettuce has been traced to at least one California farm.
The Centers for Disease Control and Prevention said on Thursday that the E. coli strain was found in an irrigation reservoir on a property owned by Adam Brothers Family Farms in Santa Barbara County, CA.
Romaine lettuce from the farm is no longer available for sale, the CDC said.
Despite the announcement, other possible sources of the outbreak are still being investigated.
"We cannot say how many cases are linked to this specific farm at this time," Ian Williams, chief of the CDC's outbreak response and prevention branch, said at a press briefing. "We have to do additional work at this farm and other farms that are being identified from our investigation."
The CDC advises people not to eat romaine grown in California’s Monterey, San Benito and Santa Barbara counties until the investigation is complete.
However, properly labeled romaine grown outside those counties and harvested after Nov. 23 is OK to eat, as well as romaine grown in greenhouses or hydroponically.
As of Dec. 13, 59 people in 15 states and Washington, D.C., have been infected by the strain of E. coli.