* BP, Shell, Statoil say cooperating with investigation
* Involves price assessment by reporting agency Platts
* Statoil says may involve pricing since 2002
By Peg Mackey and Nerijus Adomaitis
LONDON/OSLO, May 14 (Reuters) - European authorities haveraided offices of oil majors Shell, BP and Statoil in aninvestigation of suspected manipulation of oil prices, one ofthe biggest cross-border actions since the Libor riggingscandal.
Authorities have sharpened scrutiny of financial benchmarksaround the world since slapping large fines on some of theworld's biggest banks for rigging interest rate benchmarks.
On Tuesday, the European Commission said it wasinvestigating major oil companies over suspectedanti-competitive agreements related to submission of prices toleading oil pricing agency Platts, a unit of McGraw Hill Group.
"Officials carried out unannounced inspections at thepremises of several companies active in and providing servicesto the crude oil, refined oil products and biofuels sectors,"the Commission said. The inspections took place in two EU memberstates and one non-EU country, it said.
"The Commission has concerns that the companies may havecolluded in reporting distorted prices to a price reportingagency to manipulate the published prices for a number of oiland biofuel products," it said.
The Commission also said companies may have prevented othersfrom participating in the price assessment process, with a viewto distorting published prices.
Statoil said the suspected violations were related to thePlatts price assessment process and may have been ongoing since2002.
The probe will shine a light on the methodology designed byPlatts for daily assessments on the physical oil markets, usedto close deals worth billions of dollars.
The so-called Platts window, or market-on-close (MOC)system, is a daily half-hour period in which it determines cashprices through a series of bids, offers and trades.
Critics say the system is only a snapshot of the market,because it excludes trade outside the window - one reason thatit can be vulnerable to manipulation.
PRICE DISTORTIONS
The Commission said that even small distortions of assessedprices may have a huge impact on the prices of crude oil,refined oil products and biofuels purchases and sales,potentially harming final consumers.
It added the fact inspections had been carried out did notmean the companies were guilty of anti-competitive behaviour.
The Commission did not make clear whether it wasinvestigating a specific incident. These investigationstypically take years to draw final conclusions.
Platts, Royal Dutch Shell, BP and Statoil said they were cooperating with the probe.
French major Total said there had been noinspections at its offices. The Commission did not list thecompanies being investigated, and it was not clear whether othercompanies were included.
Statoil said authorities had inspected its office inStavanger on the request of the European Commission onsuspicions of anti-competitive behavior.
The Norwegian state, the controlling shareholder of Statoil,said the probe was a matter for the company's management tohandle and declined further comment.
Platts said the European Commission had "undertaken a reviewat its premises in London this morning in relation to the Plattsprice assessment process".
The International Organisation of Securities Commissions(IOSCO) is running a wider review of benchmarks, and the U.S.Commodity Futures Trading Commission is looking into the settingof old and silver prices in London.
IOSCO said it was not involved in the oil enquiry, and theCFTC had no comment.
Thomson Reuters, parent of Reuters news, competeswith Platts in providing news and information to the oil market.