A woman was caught in southern Vietnam on October 22 when trying to sedate a person for robbery.
Nguyen Thi Be, who once killed a victim with her strong anesthetic, was detained in Can Tho pending criminal charges.
The 51-year-old deputy director of a local guard company told police that she has committed nearly 30 successful anesthetic robberies in Can Tho and nearby provinces in the past two months.
She has stolen cash and cell phones worth approximately VND100 million (US$4,770).
A robbery in August 2011 killed a 59-year-old victim with overdose, police found.
Be said her trick was to approach old men on the street, and they would call her soon after for an appointment to chat or more at hotels. She would secretly put the anesthetics in the victims' drinks.
Police said Be has used a strong tranquilizer, which can render someone unconscious in five minutes and can easily kill a person.
Police also said they found many victims' gold rings at Be's house.