SAN FRANCISCO >> California health officials sent out a medical alert earlier this month after tracing the mercury poisoning of a 39-year-old Alameda County woman to an illegal skin-lightening cream smuggled in from Mexico.

Health investigators are currently going undercover in some San Francisco Bay Area ethnic communities to root out the foreign-made products whose pigment-busting ingredient can have damaging health effects. The unlabeled jars of mercury-laced cream are typically used to lighten skin or fade freckles and age spots.

California officials worked with the Centers for Disease Control and Prevention in reporting last month that at least 22 people in five households in California and Virginia had shared skin-lightening creams made in Mexico. Twelve people in California and 10 in Virginia had elevated levels of mercury in their bloodstream.