But the Federal Electoral Institute, known as IFE, said despite claims of fraud in areas where races were tight it is unlikely a recount would close the 6 percentage point gap between presidential victor Enrique Peña Nieto of the Institutional Revolutionary Party (PRI) and first runner-up Andres Manuel Lopez Obrador of the leftist Democratic Revolutionary Party (PRD).
With nearly all of the votes counted, the preliminary figures had Peña Nieto at 38 percent and Lopez Obrador at 32 percent.
While the recount isn't likely to upset the outcome of the presidential race, it could affect the makeup of the next 128-seat Senate or 500-seat Chamber of Deputies. In all, votes cast in 78,012 ballot boxes out of 143,000 will be reviewed. IFE said the audit would be completed before Friday.
This is an exercise in openness and transparency, Edmundo Jacobo, IFE executive secretary, told the Associated Press.
Lopez Obrador, who lost by a tiny margin in the 2006 presidential race that brought in Felipe Calderon of the conservative National Action Party to power, called for a recount, but IFE said it was rules instituted in 2006 that initiated the recount.
Under those rules, any polling booth count can be contested where the gap between the leading contenders of a race is less than 1 percent, when all votes at one ballot box were for the same candidate or when rejected ballots represent a figure greater the margin of loss between the leading candidates.
Sunday's election included elections for new representatives in both houses of congress, six gubernatorial races, mayor's positions in key cities as well as the office of president where the incumbent is prohibited by the constitution from running for re-election.
Lopez Obrador, a longtime leading leftist and former Mexico City mayor, accused the PRI of overspending. The two major television networks, Televisa and TV Azteca, where lambasted by the left for their favorable treatment of the PRI candidate throughout the campaign.