Paris, France - Simone Biles made a stunning return to Olympic competition on Sunday, powering through left calf pain to get her multiple-medal bid off to a rousing start.

The Team USA superstar, aiming to add to the four gold medals she won in Rio de Janeiro in 2016, tweaked her left calf warming up for her second apparatus, the floor exercise.

It didn't stop her from soaring through her signature Yurchenko double pike vault – now known as the Biles II – which, even with a big step back on landing, earned a 9.4 for execution for a massive total of 15.800 points.

She had another step back landing her second vault, but laughed as she crawled back towards her teammates on her hands and knees.

That was all it took for Biles's coach, Cecile Landi, to know that for Biles, "It's on. It's OK."

Landi, who said Biles aggravated a minor injury she'd been dealing with for a couple of weeks, said there was never any question the superstar gymnast would not continue.

"Never in her mind, no, no. Just no," Landi said, adding that she was also confident Biles would be ready to go for the team final on Tuesday and the individual events to follow.

Landi said Biles was already feeling better by the time she closed out her day by sticking the landing on her uneven bars routine – receiving another huge ovation and beaming as she shared a dance with teammate Jordan Chiles.

With two of the five qualifying sessions complete, Biles topped the all-around standings with 59.566 points.

"It was pretty amazing, 59.5," Landi said. "Not perfect, so she still can improve... just really good."

Teammate Suni Lee – the Tokyo Olympics all-around champion – was in second – a promising start for the US team as they vie to regain team gold after settling for silver in Japan.

At the end of their session, Team USA was assured of a team finals berth with a score of 172.296 points.

Italy was in second, China in third, and Britain in fourth. Team medal contenders Brazil and France were scheduled to compete later.

Brazil, led by Tokyo vault gold medallist Rebeca Andrade, won world championships silver behind the US last year.

France, led by Melanie De Jesus Dos Santos and three-time Olympian Marine Boyer, boasts one of their strongest Olympic squads ever.

But Biles remains the benchmark.

"She's just out of this world, isn't she?" British gymnast Ruby Evans said. "We've never had anyone like her before, and I don't think we ever will, ever again."

Biles led the vault and floor exercise standings and was second in balance beam behind China's Zhou Yaqin. Her eighth spot in uneven bars meant she could miss out on the eight-woman final of that event.

Biles withdrew from multiple events at the Tokyo Games as she battled the disorientating mental block that gymnasts call "twisties."

She still went home with a silver and bronze and was lauded for speaking openly about mental health struggles.

After two years away, Biles returned to win four world titles last year, taking her tally to an astonishing 23.

At 27, she could become the oldest women's all-around Olympic champion in 72 years and just the third woman to capture more than one Olympic all-around title.

Chants of "U-S-A" rang out at Bercy Arena even before gymnasts made their entrance for the second session of qualifying, and the roar when Biles was introduced was deafening.

She crushed every element in her opening balance beam routine, roaring through her aerial skills and spins without a wobble.

It was then she appeared to hurt herself warming up for the floor exercise, but after having her left leg taped from calf to foot, Biles delivered a dynamic floor routine that featured both her Biles I double layout with half a twist and her Biles II "triple-double" of two back flips with three twists.

"It's incredible," US team technical lead Chellsie Memmel said. "What she was able to do looking like she has soreness or something in her leg is remarkable."