PORT-AU-PRINCE, Haiti – U.N. police went to a garbage dump near the Haitian capital on Wednesday to recover election materials, including numbered bags apparently used to carry results and tally sheets, amid charges that last week’s presidential election was marred by fraud.

Thousands of ballots, including some that were marked, were strewn over about an acre at the dump.

Reporters saw hundreds of empty ballot boxes, at least one vote tally sheet and several empty bags – numbered and signed by the heads of polling stations – strewn across the fly-infested dump five miles north of Port-au-Prince.

“That’s extraordinary,” U.N. spokesman David Wimhurst said.

Catherine Sung, a U.N. electoral adviser who works at the main vote tabulation center, said the discovery of empty bags was troubling because they were not supposed to be thrown out.

When shown photographs of the bags, Sung said three of them were the kind used to carry invalid and blank ballots.

“They’re supposed to be kept,” she said.

A man picking through the dump, Jean-Ricot Guerrier, said the material was dumped by a truck the day after the election, and someone tried to burn the material before rain put out the fire.

Leading candidate Rene Preval claims that the Feb. 7 vote was marred by “massive fraud or gross errors” designed to leave him just short of the majority needed for a first-round victory. Preliminary results from the first election since Jean-Bertrand Aristide’s ouster two years ago showed Preval, a former Aristide protege, with a sizable lead.

A wave of chaotic protests by Preval supporters sent foreign diplomats scrambling for peaceful solutions. Preval, a former president, has urged the protesters to continue peacefully.

Ambassadors from countries “directly involved in the crisis” were discussing a Brazilian plan to persuade other candidates to recognize Preval’s victory and prevent a mass uprising, according to Marco Aurelio Garcia, foreign affairs adviser to Brazilian president Luiz Inacio Lula da Silva.

In New York, the U.N. Security Council urged Haitians to respect election results and refrain from violence, and it extended the Brazilian-led U.N. peacekeeping mission for six months through Aug. 15.

The United Nations provided security for the vote and helped ship election returns to the capital, but it is not directly involved in counting ballots.

A popularly elected government with a clear mandate from the voters is seen as crucial to avoiding a political and economic meltdown in the Western Hemisphere’s poorest nation. Gangs have gone on kidnapping sprees, and factories have closed for lack of security.

Of the 2.2 million ballots cast, about 125,000 were declared invalid because of irregularities, raising suspicions among Preval supporters. Another 4 percent were blank, but were still added into the total, making it harder for Preval to obtain a majority.

The most recent results posted on the electoral council’s Web site Monday showed Preval had 48.76 percent of the vote, with 90 percent of the ballots counted. He needs 50 percent plus one vote to win outright.