Wood Group is being investigated by the UK's financial watchdog following an independent review which found "cultural failings" with its accounting practices.
The Financial Conduct Authority (FCA) probe will look into the period between January 2023 and November 2024.
A spokesperson for the Aberdeen-headquartered engineering giant said the company would cooperate fully with the investigation.
It comes after Wood announced in March that an independent review had found “material weaknesses and failures in the Group’s financial culture”.
Wood said it was having to adjust its accounts from the past three financial years after the review.
The statement in March also said: “The cultural failings appear to have led to instances of information being inappropriately withheld from, and unreliable information being provided to, Wood’s auditors.”