The European Commission announced an investigation into Meta's handling of political advertising on its Facebook and Instagram platforms on Tuesday ahead of the June 6-9 EU elections.
EU officials are concerned that the US technology company's handling of political content risks undermining the democratic process of the European Parliament elections.
Fears are rife that deliberately misleading content from outside actors could interfere with the fairness of the European elections.
The probe is taking place under the European Union's Digital Services Act (DSA), an online content moderation law.
The powerful EU legislation requires large platforms like Meta's Facebook and Instagram to manage the risk of their services harming the electoral process, among other things.
Social media platforms are vulnerable to manipulation and foreign interference, "in particular in the run-up to elections," EU Internal Market Commissioner Thierry Breton said in a statement.
Ahead of the EU-wide elections, the commission released guidelines for how it expects large online platforms like Meta and X, formerly Twitter, to tackle disinformation.
The guidelines called on platforms to set up in-house teams to monitor local risks and to tailor their efforts to each specific election and country.
Although the DSA requires that platforms mitigate the risk of "negative effects" on elections, it does not say they have to remove disinformation.
Neither do the new guidelines. For example, they recommend "prompts and nudges urging users to read content and evaluate its accuracy and source before sharing it."
Under the DSA, platforms also have to have systems in place for users to report illegal content.
Most large platforms have signed a voluntary code of practice on disinformation, which emphasizes ensuring their systems don't promote misleading content or reward it with advertising revenue.
X withdrew from the code in May last year. The commission opened an investigation into X in December for possible breaches of the DSA, particularly after the Hamas terrorist attack on Israel in October.
The DSA's risk mitigation rules apply to platforms with more than 45 million users per month and took effect in August 2023.
Under the DSA, the commission may fine platforms up to 6% of their global revenue if they fail to address such risks adequately.
In March, the EU passed a new political advertising law, which establishes rules on transparency - such as who's funding the advertising - and on the use of personal data to target political advertisements at particular audiences. But most of the new law's rules don't come into force until late next year.
Elections to the European Parliament are due to be held between June 6 and 9.