Mexico City ? Electoral officials fanned out across the country Wednesday to begin a partial recount in Mexico’s tight presidential election, while leftists alleging vote fraud blocked bank headquarters in the capital and vowed to take their disruptive protests nationwide.

Guarded by soldiers and monitored by electoral judges and representatives of all of Mexico’s five political parties, authorities started sifting through ballots cast at 11,839 polling booths, about 9 percent of the 130,000 booths used during the July 2 election.

The count must finish by Sunday. The Federal Electoral Tribunal will review the results and can then declare a president-elect by Sept. 6, annul the election or order a greater recount.

The initial results gave Felipe Calderon, the pro-business candidate of conservative President Vicente Fox’s National Action Party, a lead of 240,000 votes, or less than 1 percent, over leftist candidate Andres Manuel Lopez Obrador, former mayor of Mexico City.

The partial count could change those results, but it was considered unlikely to tip the balance in favor of Lopez Obrador, whose supporters have been disrupting life in the capital for more than a week to press their charge he was robbed of an election victory by fraud.