Technology giants Facebook, Twitter, and Google were unable to say Wednesday if they made money from legitimate advertisements that ran next to Russian propaganda.

Sen. Kamala Harris, a Democrat who represents Silicon Valley's home in California, asked the three companies respective general counsels on Wednesday during a Senate Intelligence Committee hearing on Russia's use of social media during the 2016 U.S. presidential election if they profited from those posts.

"How much money did you make off of legitimate ads that ran alongside the Russian propaganda," Harris asked relating to Facebook, Twitter, and YouTube (which is part of Google).

All three representatives said they did not know and would have to follow up with her.

Having no such answer is “difficult to understand," Harris said, adding, “With great success comes great responsibility."

Harris had the 10-Q forms of all three companies — a quarterly report that the Securities and Exchange Commission mandates publicly traded corporations file — and noted all three have said they generate nearly all of their revenue through advertisements.

When markets close Wednesday, Facebook is expected to release its third-quarter earnings.