SAN FRANCISCO — When Christine Blasey Ford testified before Congress last month about Justice Brett M. Kavanaugh’s alleged sexual assault, an online news site called Right Wing News sprang into action on Facebook.

The conservative site, run by the blogger John Hawkins, had created a series of new Facebook pages and accounts over the last year under many different names, according to Facebook.

After Dr. Blasey testified, Right Wing News posted several false stories about her — including the suggestion that her lawyers were being bribed by Democrats — and then used the network of Facebook pages and accounts to share the pieces so that they proliferated online quickly, social media researchers said.

On Thursday, Facebook said it had identified 559 pages and 251 accounts run by Americans, many of which amplified false and misleading content in a coordinated fashion. The company said it would remove the pages and accounts. Among them were Right Wing News, which had more than 3.1 million followers, and left-wing pages that included the Resistance and Reverb Press, which had 240,000 and 816,000 followers.

Facebook said it would be the most domestic pages and accounts it had ever removed related to influence campaigns. The company said it had discovered the activity as part of its broader effort to root out election interference and because the pages had become more aggressive in using tactics like fake accounts and multiple pages to make themselves appear more popular.

“If you look at volume, the majority of the information operations we see are domestic actors,” said Nathaniel Gleicher, Facebook’s head of security. He added that the company was struggling with taking down the domestic networks because of the blurry lines between free speech and disinformation.