Amazon.com Inc.'s /zigman2/quotes/210331248/composite AMZN -0.43% business practices are being investigated as part of an inquiry by California authorities, according to a Wall Street Journal report Friday. The report, citing people familiar with the matter, says the state is examining how Amazon treats sellers in its online marketplace, including the company's practices for selling its own products in competition with third-party sellers. Amazon was not immediately available for comment. The reported inquiry comes as Amazon faces antitrust scrutiny from the Federal Trade Commission and European Union. Amazon shares declined 0.5% in trading Friday.