ChainCatcher reported that according to the Financial Times, Brussels is investigating whether Telegram has violated the EU's digital regulations by failing to provide accurate user numbers, and officials are pushing to put the controversial instant messaging app under stricter supervision.

EU legal and data experts suspect the app has underreported its user numbers in the EU to stay below the 45 million threshold above which large online platforms become subject to a raft of Brussels regulations aimed at limiting their influence.

The EU investigation runs parallel to a broad French probe into alleged criminal activity on Telegram, which led to the arrest of its founder, Russian-born billionaire Pavel Durov, on Saturday. A magistrate will decide on Wednesday evening whether to bring charges or release him.

Telegram said Durov, who now holds French and Emirati citizenship, had "nothing to hide".

Telegram said in February that it had 41 million users in the EU. Under the EU’s Digital Services Act (DSA), Telegram was supposed to provide updated figures this month, but it did not, announcing only that its “average number of monthly active users in the EU is well below 45 million.”

Two EU officials said the failure to provide new data put Telegram in violation of the DSA, adding that an EU investigation might find the real figure was higher than the threshold set for "very large online platforms".

Such a designation brings with it greater compliance and content review obligations, third-party audits, and mandatory data sharing with the European Commission.