Shell and Halliburton quizzed over Nigeria 'corruption'
Nigerian anti-fraud police are set to question the local managing directors of Shell and Halliburton.
Both companies were investigated by the US Department of Justice over their alleged roles in bribery scandals in countries including Nigeria.
Now "we are looking at the Nigeria end of things", said a spokesman for Nigeria's anti-fraud police.
Shell says it is innocent but will co-operate. Halliburton could not immediately be reached for comment.
"The [local] managing director of Shell and that of Halliburton are to appear in our Lagos office today for questioning over bribery cases," said Femi Babafemi, a spokesman for Nigeria's anti-graft Economic and Financial Crimes Commission (EFCC).
"Apart from these two chief executives, there are 21 other people, both expatriates and Nigerians, that are to appear in Abuja today for questioning over the scandals," he said, according to Agence France Presse.
US plea deal
Earlier this year, Shell was told to hand over a $30m (£19m) criminal fine for paying money to a company that in turn bribed Nigerian customs officials.
Despite maintaining that it is innocent, it was also forced to pay a further $18m of profit and interest as part of a US plea deal.
Now Nigeria's anti-fraud police - the Economic and Financial Crimes Commission - say new developments in the case mean they want to question Shell's managing director in Nigeria, Mutiu Sunmonu.
A Shell spokesman said they would fully co-operate with the police, said the BBC's Caroline Duffield in Lagos.
Separately, the managing director of Halliburton in Nigeria has also been asked to attend an interview.
Halliburton is being probed over a scandal involving the Nigeria Liquefied Natural Gas Company.
Senior executives of Halliburton - and two other companies, Saipem Construction and Technip - were arrested and then released last week.
KBR last year pleaded guilty to paying $180m in bribes to Nigerian officials prior to 2007, when it was a subsidiary of Halliburton. The firm agreed to pay $579m in fines related to the case in the US.
But Nigeria, France and Switzerland are now conducting their own investigations into the case.
The two firms have now split, and Halliburton says it is not connected with the case against KBR. It has complained that the raid on its office last week had no legal basis.
Halliburton could not immediately be reached for comment on whether its executive will co-operate with the EFCC.
Nigeria is a member of the oil cartel Opec and is one of the world's biggest oil exporters.