An unfinished overpass being built for the World Cup collapsed in Brazil's southeastern city of Belo Horizonte on Thursday, killing at least two people and injuring 19.

Globo television images showed the front of a yellow bus crushed under a large stretch of the fallen highway, which is about five kilometers (three miles) from the city's World Cup stadium and was being built as part of delayed infrastructure improvements for the tournament.

"It was like an earthquake. The ground shook violently," Daniel Magalhaes, who was near the site at the time of the accident, told Globo. "I heard a deafening sound. I looked and saw the collapsed overpass."

Two people were killed and 19 injured, the mayor's office said, lowering an earlier injury toll of 22 injured.

Large-screen public TV broadcasts here of Brazil's game Friday against Colombia, in another city, Fortaleza, have been cancelled in a gesture of mourning, the mayor's office said in a statement.

Belo Horizonte is due to host a semi-final match on Tuesday between the winners of the Brazil-Colombia and France-Germany games. The latter is also to be played Friday.

A firefighters' spokesman said 13 people were rescued from the bus unscathed but the woman driver was killed.

A car was also crushed but it was not immediately known how many people were inside and what their condition was, firefighter spokesman Edgard Estevo da Silva told reporters.

"The vehicle is completely under the overpass," he said.

Two trucks belonging to the construction company were also hit but the firm said nobody was inside them at the time, Silva said.

A total of 14 firefighting teams were at the scene.

President Dilma Rousseff expressed "sadness" on Twitter, offering her condolences to the families of victims as well as federal help to local authorities.

The structure, which was begun last year, is in the Sao Joao Batista district of the city.

"The overpass was in the final stages of construction and they were taking down the scaffolding when the accident happened," a fire brigade spokesman told AFP.

A public works spokesman for the city hall told AFP that the overpass had been due to carry an express bus service through the city. The project was supposed to have been completed at the end of July.

"All mayoralty staff have been mobilized -- the priority is to attend to the victims," said the spokesman.

Belo Horizonte's Mineirao Stadium has hosted five World Cup matches and is due to stage a semi-final on Tuesday.

The Brazil World Cup has been dogged by delays to stadiums and infrastructure, and there were several accidents during construction of the stadiums.

Just three days before the World Cup began on June 12, another accident in Brazil's business hub Sao Paulo killed one worker and injured two when an unfinished monorail collapsed.