Facebook’s second-ranking official reportedly asked the company’s communications staff earlier this year to research the financial interests of liberal billionaire George Soros.

A report Thursday evening in the New York Times, based on “three people with knowledge of her request,” said Sheryl Sandberg’s demand was a response to a Soros speech where he called for regulation of social-media giants such as Facebook and Google.

Mr. Soros told the World Economic Forum in Davos, Switzerland, in January that the internet behemoths are a “menace.”

Ms. Sandberg, Facebook’s chief operating officer, replied with an email shortly afterward to senior communications and policy executives that “told subordinates to examine why Mr. Soros had criticized the tech companies and whether he stood to gain financially from the attacks,” the Times wrote.

The email speculated that Mr. Soros might be trying to drive down Facebook’s stock price in order to profit from “short” sales.

Ms. Sandberg was at the forum, but not personally at the Soros event, the Times reported, citing a person who did attend it.

The email indicates that Ms. Sandberg was directly involved in Facebook’s efforts to counter criticism from the left over Russians efforts to use the social-media site to affect the U.S. election.

Facebook later began an opposition-research-style effort effort to make reporters aware of publicly-available information about Mr. Soros’s funding of liberal groups critical of the company.

In a statement to the Times, Facebook said the research into Mr. Soros pre-dated Ms. Sandberg’s request.

“Mr. Soros is a prominent investor and we looked into his investments and trading activity related to Facebook,” the company said. “That research was already underway when Sheryl sent an email asking if Mr. Soros had shorted Facebook’s stock.”