A European regulator has issued Elon Musk a stern warning about the spread of illegal content and disinformation on X, formerly known as Twitter, amid the Israel-Hamas conflict. Failure to comply with the European regulations around illegal content could result in fines worth 6% of a company’s annual revenue.

Thierry Breton, the European commissioner for the internal market, said in a letter addressed to Musk on Tuesday that his office has “indications” that groups are spreading misinformation and “violent and terrorist” content on X, and urged the billionaire to respond within a 24-hour period.

The letter comes after numerous researchers, news organizations and other groups have documented a rise of misleading, false and questionable content on X, creating confusion about the current conflict.