Safety fears over Chinese herbal medicines increased this week after potentially toxic substances were found in a slimming remedy sold in the UK, reports BBC Online.
The news service said that two people had to be treated for severe side-effects after taking a cocktail of remedies.
The police have launched an inquiry into the cases, and have arrested a man, although there have been no charges so far. The Medicines Control Agency which supervises drug safety in the UK is also investigating the claims, which are outlined in the British Medical Journal.
Doctors from Southend Hospital in Essex, England found traces of the banned slimming drug, Fenfluramine, both in the urine of patients who had been taking a herbal preparation, and the herbal mix itself.
Fenfluramine was banned five years ago in many developed countries owing to its ability to cause very high blood pressure in some patients.
The Southend doctors were alerted after a 44-year-old woman was referred to them suffering from high blood pressure, palpitations and anxiety.
They reported: "It became apparent that an alarming number of the local population had been attending a particular Chinese herbalist for weight loss remedies. Most had been taking multiple preparations, as many as nine, and described 'spectacular' results."
Two of the "slimming" remedies, Qian Er and Ma zin dol, were found to contain a high concentration of the banned drug.
Although the patients had recognised their symptoms to be serious, they believed that the natural origin of Chinese products guaranteed their safety.
The doctors' report emphasised the levels of naivety often associated with natural remedies.
The BBC report added that this safety alert comes after a series of incidents in which Chinese herbal remedies have been found to contain potentially harmful substances.
While herbal medicines are not regulated in the same way as pharmaceutical drugs, the MCA has launched a crackdown on certain Chinese medicines after some were found to contain a particular herb associated with kidney damage and cancer.
Other checks by the agency have found remedies containing mercury, arsenic, and prescription-only steroids.