Italian prosecutors are investigating Royal Dutch Shell PLC’s involvement in a Nigerian oil deal, a person familiar with the matter said, drawing the oil company into a corruption probe that has dogged Italy’s energy giant Eni SpA.

The prosecutors are investigating whether Shell’s piece of a $1.3 billion payment to acquire a rich oil field off the coast of Nigeria constituted a bribe, according to a person familiar with the probe. Italian and Dutch police last month raided Shell’s headquarters in The Hague looking for evidence that could be used in the case, the person said.

Shell on Wednesday confirmed it had received “notice of proceedings” from Italian prosecutors in connection with the Nigerian oil block and that its offices had been “visited” recently by Dutch authorities. The Anglo-Dutch company said it is cooperating with the investigators and is looking into the allegations.

Shell and Eni have jointly owned a Nigerian license, known as OPL 245, since 2011 to develop giant Atlantic Ocean oil fields thought to contain nine billion barrels of oil. It is a substantial project for the companies in a country that has been of historic importance to both of them.

Shell first pursued the oil fields in 2001, when it bought a stake from Malabu Oil & Gas Ltd.—a Nigerian company that was awarded the license when the African country was under military dictatorship. A new Nigerian government soon rescinded Malabu’s license, awarding Shell sole ownership and prompting years of legal disputes.