Monaco's government says it is investigating a "vast corruption scandal" implicating "numerous foreign companies active in the oil sector."
A statement from the tiny European principality said several executives of the Monaco-based company UNAOIL had been questioned over the past few days and that their homes had been searched.
Few further details were made available and Monaco's government did not immediately return messages.
UNAOIL was at the center of multi-part expose published Wednesday by the Huffington Post and Australia's Fairfax Media, which accuses the business of having "systematically corrupted the global oil industry" by delivering millions in bribes.
The publications said they drew on hundreds of thousands of emails for their six-month investigation.
A UNAOIL spokeswoman said the company "has no comment at this time."