Buhari stated this at the Nigerian Embassy in Washington while answering questions at an interactive session with Nigerians in the Diaspora.
He said evidence of looting and oil theft were being compiled by relevant agencies for possible prosecution.
He lamented that some of the affected officials were involved in illegal sale and diversion of crude oil monies belonging to the Federal Government to multiple private accounts abroad.
He vowed that his administration would trace accounts, freeze and recover the loot and prosecute the culprits.
He lamented that corruption in Nigeria has virtually developed into a culture where honest people are abused.
According to him, the Federal Government has contacted some leaders of developed nations to assist Nigeria to freeze such dubious accounts where the monies are being kept.
“We are now looking for evidences of shipping some of our crude, their destinations and where and which accounts they were paid into and in which country.
“When we get as much as we can get as soon as possible, we will approach those countries to freeze those accounts and go to court, prosecute those people and let the accounts be taken to Nigeria.
“250,000 barrels per day of Nigerian crude are being stolen and people sell and put the money into individual accounts,” he said.
According to him, the United States and others are helping the Federal Government to trace such accounts.
“The amount of money is mind-boggling but we have started getting documents.
“We have started getting documents where some of the senior people in government, former ministers, some of them had as much as five accounts and were moving about one million barrel per day on their own.
“We have started getting those documents. Whichever documents we are able to get and subsequently trace the sale of the crude or transfer of money from ministries, departments and the Central Bank, we will ask for the cooperation of those countries to return those monies to the federation accounts and we will use those documents to arrest those people and prosecute them. This, I promise Nigerians.
“A lot of damage has been done to the integrity of Nigeria with individuals and institutions already compromised,” Buhari added.
The President frowned at the way Nigerian National Petroleum Corporation, NNPC, was being managed, saying his administration would check the excesses of the corporation.
Buhari said unlike what obtained during his tenure as Federal Commissioner for Petroleum, when NNPC had only two traceable accounts before paying oil proceeds into the Central Bank of Nigeria, CBN, “everybody is now doing anyhow.”
On oil subsidy, Buhari said his administration was being careful, saying that he would not be a party to taking decision that would further bring hardship on Nigerians by removing subsidy.
He said: “When people ask you to remove subsidy, ask them to define it. Who is subsidising who? Let me make it clear. The people are gleefully saying ‘remove subsidy.’
“They want petrol to cost N500 per litre. If you are working and subsidy is removed, you can’t control transport, you can’t control market women, the cost of food, the cost of transport will rise.
“If you are earning N20,000 per day and you are living in Lagos or Ibadan, the cost of transport to work and back, the cost of food… You cannot control the market women; they have to pay what transporters charge them.
“If there is need to remove subsidy, I will study it. With my experience, I will see what I can do. But I’m thinking more than half the population of Nigeria virtually cannot afford to live.
“Where will they get the money to go to work? How can they feed their families? How can they pay their rent?
“If Nigeria were not an oil-producing country – all well and good. Our refineries are not working. We have a lot of work to do.”
On appointment of ministers, Buhari dismissed those accusing his administration of being too slow in taking crucial decisions relating to governance and appointment of political office holders.
He observed jokingly that the question was chasing him around the world even to the point that he had been nicknamed, “Baba Go Slow.”
He however noted that not even the Peoples Democratic Party, PDP, during all the years it ruled the country ever formed cabinet within the first four months.
Buhari said: “I am going to go slow and steady.”
He appealed for patience from Nigerians to allow the new administration “put some sense into governance and deal with corruption.”
On insurgency in the North East, the President said the Federal Government would only negotiate with Boko Haram if genuine and confirmed leaders of the sect came forward and convince the government of the current conditions of the abducted Chibok girls, their location and their willingness to negotiate.
He promised that his administration would at the right time tap into the enormous talents available among members of NIDO especially as consultants while their requests for voting right in 2019, a Diaspora Commission and opening of new consulates in parts of the United States and Canada would be looked into.
The President pleaded with Nigerians in Diaspora looking for government jobs back home to be patient as the economy is in bad shape, stressing that it would take about 18 months or more to fix.
All those who spoke at the interactive session expressed readiness to assist the All Progressives Congress- led administration of Buhari to achieve its campaign promises for the benefit of Nigerians.
They also called on Buhari to sign into law the Diaspora Bill.