The city's Department of Public Health said yesterday that the tea leaves bought at Sun Wing Wo Trading Company contained the plant-based toxin Aconite.
Health officials say a man in his 50s last month and a woman in her 30s this month became critically ill within an hour of drinking the tea, and both remain hospitalised.
Each person grew weak then had life-threatening abnormal heart rhythms that required resuscitation and intensive care. Aconite, also known as monkshood, helmet flower and wolfsbane, is used in Asian herbal medicines. But it must be processed properly to be safe.
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