Hong Kong consumers have been urged not to eat romaine lettuce shipped from the United States and Canada following another outbreak of the Escherichia coli infection across North America.

“For the sake of prudence, the CFS urges the public not to consume romaine lettuce from the US, Canada and unknown sources,” the  Centre for Food Safety warned, according to a government release.

This follows a similar alert by the US Centers for Disease Control and Prevention (CDCP), which advised “consumers, restaurants and retailers not to eat, serve or sell any romaine lettuce as it investigates an outbreak of E. coli”. Canada has issued a separate warning.

The CFS said it had withheld romaine lettuce imported from the two countries for testing, and the vegetable would only be released back onto the market when the results were satisfactory. It is seeking more information, including the location where the outbreak occurred.

ParknShop, Wellcome, city’super and other major retailers had voluntarily removed the lettuce from their shelves, Apple Daily said.

More than 30 people have been infected with E. coli in 11 American states, with 13 requiring hospital treatment. In June at least 200 people fell ill from an identical outbreak, and five subsequently died. There was also an outbreak in 2017 that left 25 people ill in the US.

The causes of the earlier incidents were never confirmed, and the CDCP has not yet traced the source of the current outbreak either.