Police officials in Monaco raided offices and homes of officials from oil company Unaoil on a request from the United Kingdom after allegations of corruption, involving several foreign companies. The large-scale corruption was revealed in a joint report Thursday by Australia's Fairfax Media and the Huffington Post which said that Unaoil and its owners — the Ahsani family — used multi-million dollar commissions to bribe corrupt government officials in oil-rich countries to win contracts for companies like Texas-based oilfield services giant Halliburton, its former subsidiary KBR, U.K.-based automaker Rolls-Royce, South Korean conglomerate Samsung and automaker Hyundai.

Monaco government said in a statement on its website, cited by Reuters, on Friday that the U.K.’s Serious Fraud Office (SFO) had sent an urgent request for international assistance in criminal matters. The joint report by the two media outlets said the U.S. Department of Justice, anti-corruption police in the U.K. and Australia had started a joint investigation into the dealings of Unaoil. Although the Reuters report said the company has not yet commented on the scandal, the Thursday joint report said the company denied any wrongdoing.

“Monaco authorities conducted searches of the homes of the leaders of the company Unaoil and at its headquarters in the Principality,” the statement from Monaco’s government said, according to Sydney Morning Herald, adding: “The leaders of this company were also interviewed on 29 and 30 March 2016. These searches and interviews were conducted in the presence of British officers, in connection with a case of vast corruption with international ramifications that involves many foreign companies active in the petroleum sector.”

The statement added: “The items collected during the search will be now be used by the British authorities in their investigations.”

The joint report, titled “World's Biggest Bribe Scandal,” said bankers in New York and London helped launder Unaoil’s money while the company’s owners also built a major property investment firm in central London. The report added that officials in Iraq, Iran, Libya, Syria, Yemen, Kuwait, the United Arab Emirates, Kazakhstan, Azerbaijan, Turkmenistan and Uzbekistan were involved in the corrupt dealings by Unaoil. The report also said that managers from Italian oil giant Eni, Spanish engineering, procurement and construction company Tecnicas Reunidas, French engineering company Technip and U.S. drilling giant MI-SWACO — part of Schlumberger Limited — “not only actively supported bribery but were offered or pocketed their own kickbacks.”

The report added that U.S. defense giant Honeywell and Australian subsidiary of engineering and construction services company Leighton Offshore “agreed to hide bribes inside fraudulent contracts in Iraq.” The report added that mails to Unaoil’s chief executive, Cyrus Ahsani, revealed that individual managers and executives at Halliburton and its former subsidiary Kellogg, Brown & Root knew, or had doubts, about Unaoil working in a corrupt manner to win contracts in Kazakhstan.

However, the report added that the companies working with Unaoil insisted they have “strong anti-corruption policies” and are “committed to investigating their dealings with Unaoil.”

The report also said it found out about the bribery though hundreds of thousands of leaked emails from Unaoil in the “biggest leak of confidential files in the history of the oil industry.”