The issue focused on technology companies like Facebook and Google that use technology to sell advertising to customers. The Justice Department asked Facebook to address possible violations of its users' privacy by providing data on how many times its technology services were used in research and reporting to users.

While Facebook said it would review the request, it did not respond to any specific questions from The Wall Street Journal.

And Google said it would study the request and give its answer as soon as possible.

In their letter, the