The U.S. Department of Justice has opened an investigation into whether drugmakers including Sanofi SA failed to disclose to the federal government information about the potential presence of a probable carcinogen in the heartburn drug Zantac.

Sanofi and GlaxoSmithKline in separate filings with the U.S. Securities and Exchange Commission on Wednesday said they received civil investigative demands from the Justice Department last month seeking information related to Zantac.

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