Update, 3:31 p.m.: U.S. National Security Council spokesperson Caitlin Hayden issued the following statement regarding Campos' death:

We were deeply saddened to learn of the plane crash that appears to have taken the life of Brazilian Presidential candidate Eduardo Campos as well as his travel companions. We extend our profound condolences to the family and other loved ones of the deceased and to the people of Brazil. The thoughts and prayers of the American people are with Brazil on this tragic occasion.

Original story:

A private jet reportedly carrying Brazilian presidential candidate Eduardo Campos crashed Wednesday in the city of Santos, a member of Campos' political party said.

A local official told Brazil's Globo News Campos has died. The Jornal de Hoje reported bad weather in the region, and that the plane also carried Campos' wife and son.

The tweet below translates to "Brazilian presidential candidate Eduardo Campos dies after plane crash in Santos."

Witnesses said smoke is billowing from the crash site in a residential area of Santos. A police spokeswoman told the Agence France Presse there were "fatalities but we still do not have a number confirmed." Firefighters told the BBC there were 10 "victims" but have not determined whether they're injured or dead.

Guilherme Zeinum, a resident near Santos, told Brazilian news site G1 what he saw of the crash. "I heard a loud noise, followed by an explosion. I went to the window and I could just see black smoke," he said. "I heard a noise like a turbine. It took a little while, about 10 minutes before I heard sirens heading towards the site."

According to an Air Force statement, the plane lost contact with air traffic control while preparing to land. The Cessna 560XL plane had taken off from Rio de Janeiro's domestic airport and was heading to the city of Guaruja, near Santos.

Campos' running mate, Marina Silva, was not on board the plane, a source inside the political party told Reuters.

Campos had been running for president for the Brazilian Socialist Party, with the election due to take place in October. He had formerly been a governor of the northeastern state of Pernambuco as well as the minister of science and technology under former President Luiz Inacio Lula de Silva, and is one of three forerunners, with current polls putting him third behind both incumbent Dilma Rousseff and Aecio Neves, of the Brazilian Social Democracy Party.

Immediately following news of the crash, stocks in Brazil plunged. The country's stock market had been rallying up 26 percent since the year's lowest figures in March, as analysts speculated Rousseff would be defeated in the upcoming election. With a defeat, the new government would reduce intervention in state-owned companies.

"If Campos doesn't run, all the polls we've seen so far become worthless," Rogerio Freitas, a partner at hedge fund Teorica Investimentos, told Bloomberg. "Elections are the main driver for the market now, but without Campos, uncertainty increases. And market will only find a direction once new polls become available."

The 49-year-old Campos had run on a business-friendly leftist platform, and had been a former ally to Rousseff before gunning for the presidency himself. In a November interview with The Economist, Campos spoke of his political goals:

Good management depends heavily on new politics. Distributing bits of wealth in complicity with political forces that are behind the times will never lead to good management of public resources. It will always lead to a lack of money that will be plugged by dipping into taxpayers' pockets or company coffers.