BUZZ-PureCircle: U.S. impounds co's low-calorie sweetener
** Sweetener maker PureCircle (LSE: 3571906.L - news) 's shares down 12 pct pct, worst day since listing last October, after the U.S (Other OTC: UBGXF - news) . seizes low-calorie sweetener stevia imported from China
** U.S. Customs and Border Protection says it obtained information that stevia was produced by convict labour
** PureCircle disputes allegations, but says depending on duration of detention order sales and profit could be impacted
** Shares (Berlin: DI6.BE - news) at 5-mth lows (venkateshasoumithri.mamidipudi.thomsonreuters.com@reuters.net)