By Neal Wallace

Two high-rise buildings in Rio de Janeiro, Brazil, have collapsed, covering the street with masonry and debris.

Officials have said that up to 11 people are trapped inside, while a further five have already been rescued.

It is still unclear as to what caused the collapse, but witnesses spoke of an explosion and a strong smell of gas. The city's mayor Eduardo Paes said that rescue efforts were the priority and any cause will be looked into later.

According to the BBC's Paulo Cabral, a cleaner was pulled from inside one of the elevators in the rubble after he managed to call a friend on his phone.

The buildings, which are located near the Municipal Theatre and the headquarters of oil giant Petrobras, crushed a four-story construction site on their way down.

A gas explosion in a Rio restaurant last year caused mass destruction, killing three people.