The aftermath of Yahoo’s data breach has raised a number of questions from customers, law enforcement, and most recently six U.S. Senators.

Yesterday, Senators Patrick Leahy, Al Franken, Elizabeth Warren, Richard Blumenthal, Ron Wyden, and Edward J. Markey sent a letter to Yahoo CEO Marissa Mayer, demanding answers about the company’s data breach. The letter came just days after Yahoo publically confirmed that in late 2014 a “state-sponsored” hacker stole personal information from at least 500 million customers.

The letter highlights the fact that Yahoo took nearly two years to uncover and disclose the breach, during which time “millions of Americans’ data may have been compromised.” Now the Senators want to know exactly what happened over the last two years, when and how Yahoo was first put on notice that there may have been a breach; what protection Yahoo is providing to customers whose information was compromised; and Yahoo’s plan to prevent a future breach, to name a few.

Yahoo has not yet issued a statement in response to the letter. We will continue to monitor the Senators’ inquiry.