Italian prosecutors have wrapped up a probe into the head of Italian oil major, Eni, and others over alleged corruption in Nigeria, legal and judicial sources were quoted by Reuters as saying on Thursday.

The probe involves a total of 11 people, including the Chief Executive Officer, Eni, Claudio Descalzi, and a former CEO, Paolo Scaroni, as well as Eni itself and Royal Dutch Shell.

Oil Prospecting Licence 245, an offshore oil block in Nigeria, was said to have been purchased in 2011 by Shell and Eni for $1.3bn. But corruption scandal trailed the transaction.

Under Italian law, those under investigation have three weeks to show why they should not be charged. Prosecutors gave no indication they intended to drop the case, according to Reuters.

In February this year, Shell headquarters in The Hague were searched by Dutch police and prosecutors as part of a new strand of investigation.

In 2014, a Milan court placed Eni under investigation over the purchase of the oil block, and the prosecutors later widened their investigation to include its CEO, Descalzi.

Eni and Descalzi denied any wrongdoing, with the state-controlled oil company saying it dealt exclusively with the government of Nigeria, paid fees into a government account and did not use intermediaries for the transaction.

It was reported that Italian prosecutors were working jointly with an anti-fraud team in the Netherlands in order to determine whether the two oil companies paid bribes to obtain licences for the Nigerian site.

The OPL 245, which has been at the centre of a series of long-standing disputes, was initially awarded in 1998 by former Minister of Petroleum Resources, Dan Etete, to Malabu Oil and Gas, a company in which he was a shareholder.

The field was then sold in 2011 to Eni and Shell. According to documents from a British court, Malabu received $1.09bn from the sale, while the rest went to the Nigerian government.

The PUNCH had on Tuesday reported that the immediate past Attorney General of the Federation and Minister of Justice, Mr. Mohammed Adoke (SAN), might soon be extradited from his new home in Holland as the Economic and Financial Crimes Commission had filed charges before a Federal High Court in Abuja over his alleged role in the $1.1bn Malabu oil scam.

The Malabu oil scam, which has been under investigation for over four years, relates to the billions of dollars paid by oil giants, Shell and ENI, into a Federal Government account for OPL 245, considered the richest oil block in Africa.

The money was allegedly diverted by Adoke and paid into private accounts.

The EFCC accused Adoke of illegally transferring over $800m to Etete and his firm, Malabu Oil & Gas Limited, from a Federal Government account.

The commission also accused oil magnate, Alhaji Abubakar Aliyu, who is the Chairman of the A. A. Group and Rocky Top Services, of receiving $336,456,906.78.