Mexican electoral authorities have said they are recounting more than half the ballot boxes used in the weekend's presidential election after finding inconsistencies in the vote tallies.
Of the 143,000 ballot boxes used during Sunday's vote, 78,012 will be opened and the votes recounted, Edmundo Jacobo, executive secretary of Mexico's Federal Electoral Institute said on Wednesday.
Jacobo said the recount could be finished by Thursday.
With 99 per cent of the vote tallied in the preliminary count, Enrique Pena Nieto of the Institutional Revolutionary Party, or PRI, led with 38 per cent of the vote. Andres Manuel Lopez Obrador of the Democratic Revolution Party had 32 per cent.
The presidential front-runner expressed confidence Wednesday about the recount. "I trust that the final tally will be consistent with the preliminary count," Pena Nieto said.
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Lopez Obrador has refused to accept the preliminary vote tallies, saying the election campaign was marred by overspending, vote-buying and favourable treatment of Pena Nieto by Mexico's semi-monopolised television industry.
In an interview with Al Jazeera, Pena Nieto denied the allegations.
“None of it is true and what I say is, present the proof! Which they haven’t been able to do and no matter how hard they try to present proof, they will simply not be able to do it because they don’t exist.
“There has not been a relationship supposedly one of favouritism with the mass media. We have had a transparent relationship with the mass media I think Mexico has made democratic strides that some do not want to recognise and they do not recognise it when the results of the votes don't favour them - because we don't hear the same complaints from this same person when he was elected head of government of Mexico City.
In that instance, we had serious institutions and a trustworthy counting system. When you win it exists, and when you lose, you don't want to recognise.”
The leftist candidate said on Tuesday that his team had detected irregularities at 113,855 polling places, and called for a total recount.
Feeding suspicion of large-scale vote-buying were scenes of thousands of people rushing to grocery stores this week to redeem pre-paid gift cards they said the PRI had given them ahead of the election.
Several told reporters they had been told to turn in a photocopy of their voter ID card in order to get the gift cards.
Under Mexican election law, giving voters gifts is not a crime unless the gift is conditioned on a certain vote or is meant to influence a vote. However, the cost of such gifts must be reported, and cannot exceed campaign spending limits.
Violations are usually punished with fines, but generally aren't considered grounds for annulling an election.