The cases have prompted an investigation by police and medical authorities, and renewed calls by health experts for tighter regulation of Hong Kong's beauty industry.

"Yes, the woman aged 46 died (Wednesday morning) of septic shock," a government spokeswoman said. Three others, aged 56, 59 and 60, were in hospital with the eldest in critical condition.

Septic shock is normally caused by bacterial infection and can result in respiratory and organ failure, even death.

The four had recently undergone a complicated blood transfusion procedure at the DR beauty chain, according to government statements, in a treatment that was meant to boost their immune system and appearance.

The women paid around HK$50,000 ($6,400) for the procedure, which experts say is at best an experimental treatment for cancer patients and which has not shown to have any aesthetic application so far.

DR said in a statement on Wednesday that the procedures were carried out by a doctor who was not employed by the parlor.

The procedure required their blood to be taken to isolate and culture certain types of immune cells. These "cytokine-induced killer cells" were then injected back into the women together with their own blood plasma.

The four quickly fell ill with fever, dizziness and diarrhea. In an earlier blood sample taken from the woman who died, health officials found Mycobacterium abscessus, a superbug that is notoriously difficult to kill.

Although the direct cause of the woman's death has yet to be confirmed, experts say it is likely to have been bacterial infection.

"They now have to find out where the bacterial contamination occurred in this whole process. Did it happen when the blood was drawn, during the culture process or when it was reinjected back into the body?" said William Chui, president of the Society of Hospital Pharmacists in Hong Kong.

The cases raise fresh questions on how governments in many places in Asia regulate doctors' conduct and sale of medicines, but exercise little or no control over what goes on in beauty parlors or what goes into "healthcare" products.

In Singapore in 2002, 15 women developed liver problems and one died after consuming Chinese-made slimming pills that were later found to contain two undeclared ingredients. One of the patents, an actress, survived only after a liver transplant.

Felice Lieh Mak, a leading medical expert in Hong Kong and former chairman of the Medical Council, said: "We hope that this tragedy will result in some attempt at making a legislation, or at least work towards legislating and defining what medical treatment is." ($1 = 7.7526 Hong Kong dollars)

(Additional reporting by Christina Lo; Editing by Elaine Lies)

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