SAN FRANCISCO – The parent company of USA TODAY said it had asked the FBI to investigate a wave of fake Facebook accounts so large it accounted for half of the newspaper’s following on the social media platform.

Facebook purged millions of those fake accounts from USA TODAY and other publishers three weeks ago, the latest salvo in the social giant’s battle against scammers and spammers seeking access to its platform and its 1.94 billion users.

Those axed accounts included more than a third of USA TODAY’s approximately 15.2 million Facebook “likes” at the time. Executives of Gannett Co., parent of USA TODAY and 109 local news properties, said Thursday millions of its remaining followers also were fake, and it continued to accumulate a thousand phony followers a day.

Facebook on Friday said it’s detected additional suspicious activity since its April fake-account crackdown, some of which look similar to the campaign it disrupted in April. Others more closely resemble common fake profiles that post spam comments and attempt to look legitimate by engaging with businesses’ Facebook pages.

“After we identified the additional set of violating accounts, we notified our partners at USA Today, and are taking action against these accounts,” said 

Shabnam Shaik, technical program manager on Facebook’s protect and care team, in a statement. She declined to reveal how many fake accounts Facebook had discovered.

Facebook has said in filings with the Securities and Exchange commission that it estimates about 1% of its monthly worldwide active users are “misclassified” accounts, which it says includes both fake accounts and those that don’t abide by its terms of service, such as people creating accounts for their pets. The company believes the majority of these are outside of the United States. The company declined to say what the ratio between these types of misclassified…