At least seven people were killed and nine injured on Tuesday when a bus plunged off a bridge overlooking one of Rio’s main access roads, firefighters said.

The bus landed on its roof after falling 30ft (10 metres) onto Rio’s Avenida Brazil.

Sergio Simoes, who heads Rio state’s civil defence department, said the dead were five men and two women. He added that the number of injured was likely to rise.

He said it was unclear how many were aboard and whether any of the passengers were children.

Emergency response teams could be seen evacuating the injured from the overturned bus as rush-hour traffic stood at a standstill, with some of those hurt evacuated by helicopter.

The cause of the accident was not immediately known, but eyewitness were reported as saying that a dispute between a passenger and the driver might have helped spark the crash.

Buses are the main form of public transit in the city of six million people, despite their sometimes dubious safety records and often uncomfortable overcrowding levels.

Rio’s buses, operated by private companies, do not have seat belts, and it is not unusual for up to several dozen people at a time to travel standing up. Drivers are also known for travelling at high speeds, even in residential neighbourhoods.

With two key metro stations closed pending the extension of Rio’s subway, buses have taken on an even more crucial role in recent months and are the sole public transit option in poor neighbourhoods around the city.

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