Health officials have traced romaine lettuce blamed for E. coli illnesses in California and Canada to California grower Amazing Coachella Inc.

California Department of Public Health officials confirmed that the romaine linked to the April outbreak was grown and distributed by Amazing Coachella Inc., which is the parent company of Peter Rabbit Farms, both based in Coachella, Calif.

John Powell Jr., chief executive officer at Amazing Coachella and Peter Rabbit Farms, declined comment July 18.

The E. coli outbreak sickened at least nine people in California. Most of those victims ate at “a single unnamed restaurant” according to California public health officials. At least one case of the same strain of E. coli 0157:H7 was reported in Quebec.

Another 18 people who ate at a Jungle Jim’s restaurant in Miramichi, New Brunswick, also became ill, according to Denis Allard, deputy chief medical officer for the New Brunswick Department of Health.

“We think (the contamination) was not introduced at the restaurant level because of the other outbreaks in California and Quebec,” Allard said in early July.

The suspect romaine was distributed as whole heads, not fresh cut, according to California officials.

California health officials said the romaine was shipped to a distributor in Quebec, and also supplied to the California restaurant and the Miramichi, New Brunswick, restaurant, Jungle Jim’s. When officials investigated the growing operation, the fields had already been tilled in preparation for the next season.

“CDPH and FDA followed up at the farm but were unable to identify any issues that could have led to the contamination,” according to a statement from the California Department of Public Health. “The field had long since been harvested at the time of the investigation and all lettuce from the implicated lots had long since been consumed or disposed.”

California officials also reported they did not ask the grower to make any changes or take any additional food safety precautions. Their investigation is closed, but they said they “will continue to monitor for additional positive sample results or illnesses associated with the firm’s products.”