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Brazilian President Dilma Rousseff attends the launching ceremony of a new stage of the state-subsidized housing program at Planalto Palace in Brasilia on May 6, 2016. EVARISTO SA/AFP/Getty Images

An impeachment vote against Brazilian President Dilma Rousseff has been annulled, casting doubt over the effort to remove her from office with fewer than 100 days to go before South America's largest nation hosts the Olympic Games. Brazilian markets, already down amid investigations of rampant political corruption, took a dive after the unexpected announcement.

The acting speaker of Brazil's lower house of Congress, Waldir Maranhao, said Monday he had annulled the vote in the house last month because of irregularities. His announcement came just two days before the Senate was scheduled to vote Wednesday on whether to start an impeachment trial against the embattled president. It's now unclear if that vote will go forward, BBC News reported.

Senate leader Ronaldo Caiado said the House must respect the "sovereignty" of the Senate and that the Senate will hold its impeachment vote this week as planned, while Rousseff said she had not received official information about the decision or its consequences.

“It’s not official. I don’t know the consequences. We should be cautious,” she said.

Maranhao, who opposed the impeachment, said House members committed a number of procedural missteps ahead of the April 17 vote, including publicly announcing what their position was prior to the vote and party leaders instructing their members how to vote. It's unclear whether the annulment can be overruled by the Supreme Court, the Senate or a majority in the House.

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Maranhao wants a new vote in the House and has urged the Senate to hold off. If the Senate moves forward and starts an impeachment trial against Rousseff, she could be forced to temporarily step down for up to 180 days until a final decision is reached. Vice President Michel Temer would replace her as acting president.

Rousseff's leadership has been questioned amid a growing recession, political turmoil and widespread corruption. She denies any wrongdoing.

Maranhao took over as speaker of the House last week after the previous speaker, Eduardo Cunha, was suspended. He is under investigation for alleged corruption, intimidation of lawmakers, obstruction of justice and abuse of power and is unpopular among voters, the Guardian reported. Maranhao himself is under investigation for allegedly taking bribes and has denied all wrongdoing.

The annulment decision saw Brazil's currency drop by as much as 5 percent and Brazil's benchmark Bovespa stock index fall by 3 percent. Central bank director Altamir Lopes told Reuters the market volatility was expected given the political uncertainty.