Authorities are scrambling after reports that two people became critically ill in San Francisco after consuming tea from a Chinatown herbalist. The tea leaves, purchased from Sun Wing Wo Trading Company, apparently had the toxin Aconite in them, according to a Department of Public Health report issued on Friday.

A man in his 50s and a woman in her 30s are fighting for their life after drinking the tea and become ill within an hour, according to reports. Both are still hospitalized. The patients reported abnormal heart rhythms that required resuscitation and transfer to intensive care.

Aconite is also known as monkshood and wolfsbane, and it is often featured Asian herbal medicines, but it must be properly processed in order to remove the toxins. Health officials are trying to figure out where the tea leaves came from, and they have warned others not to consume tea from the shop.

“Anyone who has purchased tea from this location should not consume it and should throw it away immediately,” said Dr. Tomás Aragón, health officer for the city and county of San Francisco. “Aconite poisoning attacks the heart and can be lethal.”