US Senate Democrats plan to enlist accountants and legal experts to look through the business records of ExxonMobil boss Rex Tillerson.
It comes after he was revealed as President-elect Donald Trump’s pick for Secretary of State.
Concerns have been raised by both Republicans and Democrats over Tillerson’s alleged ties to Russia.
Democrats are said to want both his wealth and business interests to be put under close scrutiny.
Tillerson, 64, is on the New York Times’ list of the 200 highest-paid chief executives.
This year he earned an estimated $24.3million.