Nigeria election: The mystery of the altered results in disputed poll
A BBC investigation has found evidence suggesting some results from Nigeria's presidential election may have been manipulated.
The winner Bola Tinubu is due to be inaugurated on 29 May but the opposition is challenging this.
The BBC has uncovered significant anomalies in Rivers state, a key battleground, although not sufficient to change the overall national outcome of the election, which took place in February.
There are also questions over the identity of an election official who read out some of the unexplained results.