Editor's note: After publication of this story, a Facebook spokesman emailed to say, "It appears the Senator misspoke." That's consistent with a report from Quartz, which said Facebook began its hunt by searching for "buyers who took out potentially political ads and either self-identified as Russian, had Russian set as their language, had a Russian IP address, or paid for the ad in Russian rubles." 

Facebook is in all kinds of trouble for letting Russian agents use its platform to spread phony rumors and inflammatory messages to Americans during last year's presidential campaign and in the months since.

But not all of the disinformation originated in the Kremlin. Some of it's coming from Facebook itself.

On Thursday, Democratic Senators Amy Klobuchar of Minnnesota and Mark Warner of Virginia held a press conference to discuss the Honest Ads Act, a bill seeking to establish new standards of transparency and accountability for large internet companies that sell political advertising. A direct response to Russia's election meddling, the bill would require platforms like Facebook and Google to keep public files of all paid "electioneering communications," even those involving small amounts of money, as well as to "make reasonable efforts to ensure that foreign individuals and entities are not purchasing political advertisements in order to influence the American electorate." 

But perhaps the biggest news coming out of their presser was a throwaway comment from Warner, who suggested Facebook was going easy on itself when it announced it had discovered $100,000 worth of ads clearly linked to Russian actors and another $50,000 worth it deemed suspicious.

"I still believe that may be just the tip of the iceberg," Warner said. "Remember, these were the ads that were paid for in rubles. And we've not been able to sort through whether some of these same accounts may have been smart enough to use dollars, rubles or pounds to pay for ads. So there may be more."

Assuming Warner's statement was an accurate summation -- I've emailed Facebook's press office for comment and am awaiting a reply [Update: Faceboook says it was not accurate; see editor's note at the bottom of this post] -- the company's Sept. 6 post about the results of its internal investigation suddenly looks more like spin than an act of transparency. Facebook's head of security, Alex Stamos, described its findings as the results of a "broad search" for all "ads that might have originated in Russia -- even those with very weak signals of a connection and not associated with any known organized effort." There was certainly no indication that $150,000 could be "the tip of the iceberg," as Warner suggests. Quite the opposite.

To be sure, Facebook CEO Mark Zuckerberg left open the possibility that there could be more shoes to drop in a Sept. 21 post, writing, "We may find more, and if we do, we will continue to work with the government."

Still, if Warner is proved right, it will be the continuation of a disturbing trend in which Facebook downplays its importance as an avenue for shady influence operations by publicly stating less than it knows or suspects. Soon after the election, Zuckerberg called it a "pretty crazy idea" that Facebook had any effect on the outcome, a seemingly off-the-cuff comment that now appears to have been part of a deliberate strategy aimed at deflecting criticism. In late July, more than eight months after the election, the company was still  denying it had any reason to think Russia had used Facebook ads to sway American voters. 

The Honest Ads Act isn't perfect. Its effectiveness would depend on the willingness of the Federal Elections Commission, a body paralyzed by partisan division, to slap tech companies that spend millions on lobbying with meaningful fines. At the press conference, Warner repeatedly described it as a "light touch" measure, apparently hoping that will make it more palatable to Silicon Valley.

But Facebook's persistent efforts to be seen as accountable while evading real transparency shows why this is a problem that can't be solved through self-regulation. That would require Facebook to be its own toughest critic--not its own spin doctor.