US prosecutors have opened a criminal investigation “regarding matters” related to the ‘Panama Papers’ leak of documents that have revealed secret offshore bank accounts linked to the rich and powerful.

Preet Bharara, US attorney for the Southern District of New York, disclosed the probe by his office in a letter to the International Consortium of Investigative Journalists. In the letter, which was posted on the Guardian’s website and has been authenticated by the Financial Times, is seeking to speak with an ICIJ employee about the data leak.

Earlier this month ICIJ and other news organisation published multiple stories based on 11.5m files leaked from Panamanian law firm Mossack Fonseca, one of the largest offshore law firms. The stories revealed offshore accounts linked to David Cameron, a close friend of Russian president Vladimir Putin and Iceland’s Prime Minister Sigmundur David Gunnlaugsson, who was toppled by the revelations.