MEXICO CITY — Mexican electoral authorities said Wednesday they will recount more than half the ballot boxes used in the weekend’s presidential elections after finding inconsistencies in the tallies.

Of the 143,000 ballot boxes used during Sunday’s vote, 78,012 will be opened, and the votes recounted, said Edmundo Jacobo, executive secretary of Mexico’s Federal Electoral Institute.

Jacobo said the recount could be done by Thursday.

Mexico’s electoral law states that the votes should be recounted if there are inconsistencies in the final tally reports, when the result shows a difference of one percentage point or less between the first- and second-place finishers or if all the votes in a box are in favor of the same candidate.

With 99 percent of the preliminarty vote tallied, Enrique Pena Nieto of the Institutional Revolutionary Party led with 38 percent of the vote. Andres Manuel Lopez Obrador of the Democratic Revolution Party had 32 percent.

Officials also will recount 61 percent of the ballot boxes in the vote for the Senate and 60 percent in the vote for the lower house of Congress.