Venezuela’s powerful oil minister has quit during a probe focused on corruption linked to tanker trades at state-run Petroleos de Venezuela SA (PDVSA).

Tareck El Aissami announced on Twitter that he was leaving his post so he could support the inquiry into “serious acts of corruption” at the sanctioned oil company, which is supervised by the ministry.

Anti-corruption officials have made a series of high-level arrests focused on oil cargoes leaving the country without proper payments to the company, according to Reuters.