Volkswacht Bodensee - Dramatic fall costs Biles Olympic medal, triathletes plunge into Seine

The day after US sprinter Noah Lyles blasted his way into the record books with the narrowest of wins in the men's 100m, all eyes were on Biles to see if she could write some history of her own.

Widely considered the greatest gymnast in history, Biles was bidding to add to her Paris haul of three golds in balance beam and floor finals at the Bercy Arena.

But she slipped off the beam while walking backwards in her routine, the unusual error gifting gold to Italy's Alice D'Amato.

A clearly furious Biles exited the arena to prepare for her floor exercise final, where she could win her fourth gold in Paris and eighth overall, after snatching four in Rio in 2016.

She famously fell victim to the debilitating mental block gymnasts call the "twisties" at the Tokyo Olympics but has bounced back emphatically to silence critics who slammed her as a quitter.

- 'Food poisoning'? -

Earlier Monday, the Seine was deemed clean enough to stage the mixed triathlon relay following uncertainty over pollution levels and illness in the build-up to the race.

The race turned out to be a thriller, Germany's Laura Lindemann holding off a fierce challenge from the United States and Britain to take gold in a photo finish.

Belgium withdrew as one of their athletes fell ill after competing in the Seine on Wednesday but officials gave the all-clear for Monday's race after assessing the water.

The Swiss team also drafted in a replacement after their racer Adrien Briffod suffered a gastrointestinal infection.

Norwegian competitor Vetle Bergsvik Thorn told AFP he too had been stricken with a stomach bug after the men's race last week.

"I was sick for about 12 hours, overnight from Friday to Saturday," he said.

"I don't know if it was food poisoning or from the Seine. Obviously it wasn't the best preparation for today."

The Seine has been the focus of attention during the Games, consistently failing water quality tests despite a 1.4 billion euros ($1.5 billion) upgrade to improve the Paris sewerage and water treatment systems.

- Big favourite -

Plenty more drama is expected at the Stade de France after the closest 100m final in modern Olympic history electrified the crowd on Sunday.

In Monday's early action, the "big three" advanced comfortably in the heats of the men's 400m hurdles, seen as one of the most competitive races of the Games.

Defending champion Karsten Warholm and his challengers, American Rai Benjamin and Brazilian Alison Dos Santos, all cruised through their races and eased up well before the line.

"I think this is the second-fastest heat I have ever done. It felt very good," said Warholm, the three-time world champion from Norway.

On Monday evening the virtually invincible Armand Duplantis goes in the pole vault -- his main competitor in Paris is likely to be himself and the world record.

The main question over the Swede is just how high he can go. He set a new world record of 6.24 metres earlier this season.

On the track, Dutch distance queen Sifan Hassan runs in the final of the women's 5,000m, as she hunts a historic golden treble of 5,000m, 10,000m and marathon.

It also emerged that a noticeable delay before Sunday's 100m final was caused by an attempted pitch invasion.

- Freak accident -

In a packed day 10 schedule, track cycling begins at the National Velodrome with the first gold on offer in the women's team sprint.

Britain have topped the cycling medals table at every Games since Beijing in 2008 but are without retired greats Laura and Jason Kenny, who won 12 gold medals between them, and Katie Archibald, who broke her leg in a freak accident.

Meanwhile, South Korea's An Se-young consolidated her status as the top player in women's badminton, beating China's He Bingjiao in an exhilarating final.

The men's football tournament hits the semi-final stage, with Morocco taking on Spain in Marseille before Thierry Henry's France face Egypt in Lyon.

China moved to the top of the medals table with 21 golds, two ahead of the United States. France and Australia both have 12.

The hosts have already surpassed their record Olympic medal haul, with plenty more opportunities before Sunday's closing ceremony.

burs-ric/gj

H.Weber--VB