At least 12 people were injured when a float collapsed in Rio de Janeiro's Sambadrome, the venue where the samba schools hold their annual carnival parade.
A walkway on top of the float on which dancers were standing toppled early on Tuesday, sending them tumbling.
The incident came a day after 20 people were injured at the Sambadrome when a float crushed them against a fence.
Police are investigating both incidents.
'Moment of despair'
The float represented Bourbon Street in New Orleans and members of the samba school were dancing on walkways made to look like balconies when the upper walkway gave way.
"We heard a burst on the top. People started screaming, we didn't understand what it was," eyewitness Felix Souza said.
"It was a moment of despair for all there."
The parade was halted for 25 minutes as the emergency services took the injured to hospital.
The float belonged to Unidos da Tijuca samba school.
Its director, Aiton Freitas, said he did not know what had gone wrong.
He said the float had been tested three times a week with more weight than it was carrying during the parade.
"We are even more shocked than you all are," he told journalists. "I don't know what is happening, but Rio's Carnival is not being blessed this year."