Facebook faces probes from the European Union and the UK that could force it to pay hefty fines and change its business model.
The two have launched antitrust investigations into the social network's use of advertising data in its classified ads service.
The European Commission and Britain's Competition and Markets Authority are probing whether Facebook uses data from advertisers to compete with them.
It marks European Competition Commissioner Margrethe Vestager's first antitrust probe into the world's largest social network.
And her latest fight with one of the U.S. tech giants.
Vestager has slapped more than $9.7 billion in fines on Alphabet unit Google and is also investigating Amazon and Apple.
And she plans to focus on Facebook's vast trove of data from the near 7 million companies that advertise on it.
On Friday (June 4) she said "in today's digital economy, data should not be used in ways that distort competition".
Britain's Competition and Markets Authority also announced its own investigation.
Facebook said it would cooperate fully with both, but described the probes as "without merit".