Two people are critically ill after drinking tea bought from the same Chinatown herbalist in San Francisco.

The tea leaves bought at Sun Wing Wo Trading Company, at 1105 Grant Avenue, contained the plant-based toxin Aconite, the Department of Public Health said Friday.

A man in his 50s last month and a woman in her 30s this month became sick soon after drinking the tea, and both remain hospitalized, health officials said.

“Both patients developed symptoms about an hour after consuming the tea,” said Dr. Tomas Aragon, health officer for the city and county of San Francisco.

Each person grew weak then had life-threatening abnormal heart rhythms that required resuscitation and intensive care.

"The tea leaves were provided in a plastic bag," which was not labeled, according to Aragon.

Aconite, also known as monkshood, helmet flower and wolfsbane, is used in Asian herbal medicines. But it must be processed properly to be safe.

"This Aconite poisoning which can come from Chinese herbal teas if not processed correctly it can affect the heart. It can give them neuological symptoms like tingling it can also give you nausea and vomiting," Aragon said.

Health officials are working to find the original source of the tea leaves, and they are warning others to stop consuming it. For now, all the tea's ingredients have been removed from the store's shelves.

"Anyone who has purchased tea from this location should not consume it and should throw it away immediately," Aragon said. "Aconite poisoning attacks the heart and can be lethal."

There is no indication that the people were poisoned intentionally, according to officials.