At least two people were killed when part of an elevated bike lane, built ahead of the Olympic Games in Rio de Janeiro, was hit by a strong wave and collapsed on to the beach below, authorities in Brazil said.
Rio Municipal Secretary Pedro Paulo Carvalho said a third person was thought to be missing.
He said an investigation was under way to determine what caused the accident on the Tim Maia Bike Path, which was inaugurated in mid-January and connects the beachfront neighbourhoods of Leblon and Sao Conrado.
The structure snakes alongside a beachfront highway, perched high above the water on concrete and metal pillars set into the rocky cliff.
Mr Carvalho declined to answer questions about whether shoddy workmanship may have been to blame for the accident.
He said it appeared the approximately 50m stretch collapsed after being struck beneath by a strong wave. Ambulances were dispatched to the scene and helicopters hovered over the beach.
Rio de Janeiro is hosting the Summer Games beginning in August, and the bike lane was among the Games' legacy projects. While no Olympic event will be held on the path itself, the collapse is likely to add to concerns about the country's readiness to host the Games.
An Associated Press photographer at the scene saw two bodies laid out on the Sao Conrado beach. A woman thought to be the wife of one of the victims knelt over his body, kissing his face and begging for another moment to "say goodbye".
The two dead have not been named, but Diego Goncalves Fernandes, a beach vendor who saw the bodies floating in the water before they were fished out by a helicopter, said both were men.
A crowd of beachgoers gathered around the bodies, which were laid out on the sand and covered by colourful beach sarongs. Nearby, other beachgoers continued a game of beach soccer.
Thursday was a public holiday in Brazil and, with the weather sunny and warm, the city's bike paths, beaches and other outdoor recreational spots were packed.
Since its launch on January 17, the path has earned kudos for its spectacular views. But detractors complained that the narrowness of the path made cyclists prime targets for mugging.
In the weeks after it was opened, local newspapers also featured photos of its speedy deterioration, showing missing handrails and rusting metal parts.
The bike path runs parallel to a road high above the sea that will be used for the road-cycling event in the Olympics. Construction is under way to extend the bike path westward to the Barra da Tijuca neighbourhood which is one of the Olympic hubs.
Asked about concerns over that stretch of the bike path, Mr Carvalho said its engineering would also be subject to extra scrutiny.
The collapse happened just hours after the flame for South America's first Olympics was kindled in Ancient Olympia, the birthplace of the ancient Games.
Carlos Nuzman, the head of the Rio de Janeiro organising committee, expressed optimism in a speech at the ceremony.
"We are incredibly proud to have come so far, sailing through some of the most challenging waters the Olympic movement has seen," he said before hearing of the accident, adding that the Olympic flame "brings a message that can and will unite our dear Brazil".
The lighting of the flame heralded the start of a 15-week journey which will culminate with the August 5 opening ceremony in Rio de Janeiro.