MEXICO CITY – Thousands of people rushed to stores Tuesday to redeem pre-paid gift cards they said were given them by the party that won Mexico’s presidency, inflaming accusations that the election was marred by massive vote-buying.

At least a few cardholders were angry, complaining they didn’t get as much as promised, or that their cards weren’t working.

Some of those lined up to use their gift cards said they got them for supporting the Institutional Revolutionary Party, or PRI, whose candidate Enrique Pena Nieto won Sunday’s election, according to the preliminary official vote count. Some wore red T-shirts and baseball caps with Pena Nieto’s name printed in white.

Under Mexican election law, giving voters gifts is not a crime unless the gift is meant to condition or influence their votes.

Also, the cost of such gifts must be reported to authorities and cannot exceed campaign spending limits.

Violations of those rules are usually punished with fines but are not usually considered ground for annulling the elections.

On Tuesday, Alfredo Figueroa, a council member of the oversight agency known as the Federal Electoral Institute, said authorities are investigating the Soriana card complaint.

Figueroa also said that irregularities in vote tallies may eventually lead to the opening and re-counting of votes from as many as 50,000 polling stations, about one-third of the 143,000 involved in Sunday’s vote.

But on Tuesday, Andres Manuel Lopez Obrador – the leftist Democratic Revolution Party candidate, who came in second – said his team had detected irregularities in 113,855 polling places and called for a much wider recount.

“This is a scandal. ... They bought millions of votes,” Lopez Obrador said at a news conference, referring to the PRI. “Clearly, they far exceeded campaign spending limits; ... this is a national embarrassment.”