The plot is believed to be from mainland China, with suspects speaking Mandarin and using telephone calling cards and disposable cellular phones.
None of the victims has turned over any money.
Anyone who gets such a call is urged to call local authorities immediately. Calls have been received in Alhambra, Pasadena, San Marino, South Pasadena and San Gabriel.
Similar plots have been reported in Northern California.
Police suggest professionals limit the amount of personal information they release, use home security systems and be aware of their surroundings.
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