SAN FRANCISCO (KTVU) -- San Francisco Department of Public Health inspectors are still trying to trace the origin of a potentially deadly ingredient found in tea leaves sold at a medicinal shop in Chinatown.
Two people ended up in critical condition after reportedly drinking tea made from herbs sold at the Sun Wing Wo Trading Company on Grant Avenue near Pacific Avenue in February and earlier this month.
The incidents have raised new questions about federal and local oversight of the herbal industry, which is currently not regulated by the FDA.
Investigators say the poisonous ingredient is called aconite, which is derived from the helmet flower or plant commonly called "Monkshood."
A woman in her 50s remained in critical condition Monday after drinking the tea. A man in his 30s, who also consumed the herbs, was released from the hospital over the weekend.
"Was it in the supply chain? Was it before the ingredients ever came to the shop? Was it some contamination that happened at the shop? Was it something else?" asked Rachael Kagan, a spokesperson for the Department of Public Health.
Owners of the Sun Wing Wo Trading Company declined to comment.
A line of customers waited at the pharmacy-style shop Monday morning as customers described their ailment to the worker behind the counter, who in turn, recommends a list of herbs which are to be brewed into a tea.
The people who fell ill after consuming the tea had ordered a list of 14 and 18 ingredients for their teas. The health department's testing of blood, urine and herb samples concluded that the poison was aconite.
"I don't think it's unusual to see toxicity from aconite from herbs in traditional Chinese medicine," said Dr. Craig Smollin, an emergency physician and toxicologist who also works as the director of the San Francisco Division of California Poison Control. "It's just probably in smaller doses and for whatever reason in this particular instance, these patients got larger doses."
If processed correctly, experts say small doses of aconite are used to treat pains and bruises.
But within one hour of drinking the tea, both victims experienced symptoms such as irregular heartbeats, vomiting and dangerously low blood pressure.
"This is their culture for thousands of years that they've used these things," said Buck Adams, who visited Chinatown from Colorado recently with his girlfriend, Skye Forrest.
The pair explained that they want to be culturally sensitive but they're not familiar with the herbs in Chinatown so declined to buy any.
"It's not regulated (but) it's an herbal supplement and they're not claimed by the FDA but it's track and traceability," Adams said. "If you know the source of where it's coming from you're probably pretty safe (but) if you're just going in and purchasing something that you're not aware of you're taking a risk."
Experts say cases of aconite poisoning are fairly rare but what's less common is to see several cases pop up in proximity to each other and that can be traced back to a single vendor.
By KTVU reporter Tara Moriarty.