LOS ANGELES (MarketWatch) -- Shares of Silvercorp Metals Inc. traded in Toronto [ca:svm] and in the U.S. /zigman2/quotes/209674256/composite SVM +3.56% each tumbled 18% Tuesday afternoon following a Financial Post report that Alfredlittle.com, a publisher of short-seller research on Chinese companies, has accused Silvercorp of fraud. The Alfred Little report claims Silvercorp's production and resource estimates for the flagship Ying mine are higher than what's reported locally in China. Vancouver-based Silvercorp produces silver in China. A person contacted by MarketWatch at Silvercorp didn't offer a comment about either report. The British Columbia Securities Commission on Friday confirmed it was investigating a separate, anonymous allegation against Silvercorp. Silvercorp said Monday its cooperation with the investigation is "an important first step towards mitigating the damage done to Silvercorp's reputation."