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

At least a few cardholders complained that they didn’t get as much as promised or that their cards weren’t working. Neighbors at one store in a poor neighborhood on the outskirts of Mexico City said the unusually large crowds prevented them from doing their daily shopping.

Some people shopping at the store said that they were told the cards would be valid only during the two days after Sunday’s election and that they had waited to cash them in until Tuesday because the store was packed Monday.

Under Mexican election law, giving voters gifts is not a crime unless the gift is conditioned on a certain vote or 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.

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

Maria Salazar, a 20-year-old university student, came with her 70-year-old father, Antonio Salazar, to cash three cards.

“They gave us the cards in the name of the PRI and Rep. Hector Pedroza (a PRI congressional candidate), and they said they were counting on our vote,” Maria Salazar said outside one store, as she carried shopping bags packed with toilet paper, cooking oil, rice, crackers and instant noodle soups.

Her father carried two more packed grocery bags and her 8-year-old nephew carried another.

“They told us they were worth 500 pesos ($37.50), but when we got to the check-out, they were only worth 100 rotten pesos ($7.50),” Salazar said.

Both she and her father said they had been told to turn in a photocopy of their voter ID card in order to get the gift cards.

Another woman interviewed outside the same Soriana grocery store also complained that her card had only 100 pesos in credit.

“For helping them with votes and all … they gave us a card for supporting them, and all that for 100 pesos,” said the woman, who gave only her first name, Josefina, for fear of reprisals. She said she got the card for supporting Pena Nieto, but complained that “100 pesos lasts you about five minutes.”

Inside the store, long lines formed at card-reading machines as people tried to find the balances on their cards. Some grew angry and shouted insults against Pena Nieto.

Pena Nieto’s campaign and the PRI press office said they had no immediate comment. In the final days of the campaign before Sunday’s vote, PRI officials denied allegations that the party had distributed pre-paid cash cards from a local bank.

Humberto Fayad, a spokesman for the Soriana grocery store chain, denied the company sold huge amounts of gift cards to the PRI. “There is no agreement between the PRI and Soriana, or Soriana and any other political party. Soriana is a non-political company,” Fayad said.

Before the election, the PRI accused the conservative National Action Party, or PAN, whose candidate ran third in the presidential election, of passing out groceries during the campaign, and claimed the leftist Democratic Revolution Party, or PRD, had gotten illegal campaign financing. None of those allegations have been proven.