Rio de Janeiro: Two Russian swimmers implicated in a bombshell report on state-sponsored doping were given the green light to compete at the Olympics on Thursday as football superstar Neymar prepared to kick-off Brazil's quest for football gold.
Amid simmering political and social tensions, Brazil is also on alert for protests ahead of Friday's gala opening ceremony with heads of state from at least 45 countries expected at the Rio Olympic stadium.
Vladimir Morozov and Nikta Lobintsev, who were both implicated in the World Anti-Doping Agency report headed by Richard McLaren, are among 31 Russian swimmers confirmed to take part in Rio, world swimming body FINA said.
Although five Russian swimmers remain banned, all of the country's water-polo players, synchronised swimmers and divers have been allowed into the Games.
Russia's boxing and judo teams have also been cleared to compete. Russia could confirm the final composition of its team later on Thursday.
Italian beach volleyball player Viktoria Orsi Toth meanwhile became the first athlete to be sent home from Rio after failing a dope test.
Orsi Toth underwent a spot check on July 19 and tested positive for clostebol, an anabolic steroid, Italy's Volleyball Federation said.
A second analysis confirmed the result, the federation added.
The fall-out from the Russian drug scandal has dominated the build-up to the Games, which formally get under way with Friday's opening ceremony at the iconic Maracana Stadium.
Football legend Pele is reportedly the front-runner to light the flame at Friday's spectacular, which starts at 8:00pm (2300 GMT) and will feature Brazilian supermodel Gisele Bundchen, thousands of dancers and hundreds of VIPS.
"It's going to be a beautiful ceremony, very Brazilian, very Olympics, and very sportsmanlike," Rio 2016 spokesman Mario Andrada told a press conference on Thursday.
The ceremony could be targeted by protests directed against Brazil's interim president Michel Temer, who took over from elected president Dilma Rousseff while she battles impeachment proceedings.
Temer has said he expects to heckled when he makes a short announcement declaring the Games open. Brazilian media reports say that music will be turned up as soon as he finishes speaking to mask any booing.
The Olympic torch continued its troubled path around the host city the day after riot police fired stun grenades and tear gas against protesters in a poor northern neighbourhood angry at the cost of the Games.
Foreign dignitaries began arriving in Rio on Thursday, with French president Francois Hollande lending his support to Paris's bid to host the 2024 Games.
As Rio put the finishing touches to preparations for the Games, Brazilian football fans prepared for the tournament debut of Barcelona superstar Neymar as the men's football tournament gets under way.
Olympic gold is the only international title to elude Brazil in an illustrious history that has seen them win five World Cups.
Neymar had pushed hard to be included in the Olympic squad, two years after his World Cup campaign on home soil ended with a back injury which forced him to miss a humiliating 7-1 semi-final defeat against Germany.
"Neymar has exceeded my expectations. He is appreciated, he's a good guy with a huge heart especially around the younger players," Brazil manager Rogerio Micale said.
Brazil open their campaign against South Africa in Brasilia, one of six Olympic football host cities, before facing Iraq and Denmark in Group A.
The first gold medal should be given on Saturday in the shooting. Some 10,500 athletes are taking part in the Games which end on 21 August.