SAN FRANCISCO — On the same day Facebook announced that it had carried out its biggest purge yet of American accounts peddling disinformation, the company quietly made another revelation: It had removed 66 accounts, pages and apps linked to Russian firms that build facial recognition software for the Russian government.

Facebook said Thursday that it had removed any accounts associated with SocialDataHub and its sister firm, Fubutech, because the companies violated its policies by scraping data from the social network.

“Facebook has reason to believe your work for the government has included matching photos from individuals’ personal social media accounts in order to identify them,” the company said in a cease-and-desist letter to SocialDataHub that was dated Tuesday and viewed by The New York Times.

Facebook gave the companies until Friday to detail what data they had taken and then delete it all.

The case illustrates a new reality for Facebook. SocialDataHub and Fubutech have been around for at least four years, relying in part on Facebook data to build products that might alarm some civil-liberty advocates.