The Globe and Mail reports in its Tuesday edition that Yahoo Inc. should face a U.S. Securities and Exchange Commission investigation into whether the Internet media company properly informed investors and the public about a massive data breach, Sen. Mark Warner said in a letter to SEC chair Mary Jo White. A Bloomberg dispatch to The Globe says Marissa Mayer, Yahoo's chief executive officer, waited until last week to formally disclose that information on 500 million accounts had been compromised in the 2014 breach even though she knew about it as early as July, wrote Mr. Warner, a Virginia Democrat and co-founder of the Senate cybersecurity caucus. "A breach of the magnitude that Yahoo and its users suffered seems to fit squarely within the definition of a material event," Mr. Warner wrote in the letter dated Sept. 26. Yahoo last week announced results of an investigation that found customers' personal information was stolen in a "state-sponsored" attack in late 2014. Compromised information may include names, e-mail addresses, phone numbers, dates of birth, encrypted passwords and, in some cases, unencrypted security questions and answers. Yahoo hopes to close the Verizon buyout by early next year.