Hurdler Jasmine Camacho-Quinn claimed Puerto Rico's first Olympics athletics gold on Monday but Belarusian sprinter Kristina Timanovskaya was absent from the women's 200m after claiming her country had forced her to leave the Games.
Also on day four of track and field in steamy Tokyo, Greece's Miltiadis Tentoglou left it late to win the men's long jump while Dutch distance runner Sifan Hassan kept up her bid for an unprecedented treble on track despite falling.
Elsewhere on day 10 of competition, the track cyclists start their campaign with Britain's dominance under threat and transgender athlete Laurel Hubbard is preparing to make history in the women's weightlifting competition.
The Olympic Stadium witnessed a dramatic evening on Sunday as unheralded Italian sprinter Lamont Marcell Jacobs stormed to a shock gold in the men's 100 metres in a time of 9.80 seconds.
Attention switched on Monday to the finals of the women's 100m hurdles and the men's long jump as well as qualifying for the women's 200m and 1500m.
Camacho-Quinn, 24, who had set an Olympic record 12.26sec in the semi-finals of the 100m hurdles, surged home to claim her first major title in 12.37sec.
World record-holder Keni Harrison of the United States took silver in 12.52sec while Jamaica's Megan Tapper claimed bronze.
"For such a small country it gives little people hope," said Camacho-Quinn. "I am just glad I am the person to do that."
In the men's long jump, European champion Tentoglou leapt a best of 8.41 metres on his sixth and final attempt to snatch victory from Cuban Juan Miguel Echevarria, who also jumped 8.41m but had an inferior second-best jump.
"What an incredible competition," said Tentoglou. "What an incredible jump, the last jump. I wasn't able to get it right at the start. But in the end I managed to pull something out to get the medal."
Defending 200m champion Elaine Thompson-Herah continued her audacious bid for an unprecedented Olympic women's sprint "double-double" as the Jamaican advanced to the 200m semi-finals.
Shelly-Ann Fraser-Pryce, outgunned by her teammate in the 100m final, also progressed, but 100m bronze medallist Shericka Jackson, also of Jamaica, failed to make it through after inexplicably slowing with 40 metres to run.
Christine Mboma of Namibia, who has to run this distance because her high testosterone levels mean she is barred from the 400m, clocked the fastest time, 22.11sec, to finish ahead of hot US favourite Gabby Thomas.
Belarusia's Timanovskaya was supposed to be competing in the 200m heats but instead spent the night in a Tokyo airport hotel.
Officials said the 24-year-old sprinter, who claimed her team was forcing her to return home after she criticised the athletics federation, spent the night under protection and may be seeking asylum.
Distance runner Sifan Hassan kept alive her hopes of an unprecedented Olympic treble of 1500, 5,000m and 10,000m after picking herself up to win her 1500m heat following a potentially disastrous fall.
Away from the action, US shot putter Raven Saunders has risked disciplinary action after making the first protest on a medal podium of the Olympics.
The 25-year-old African-American athlete crossed her arms in an "X" gesture during Sunday's medal ceremony after claiming silver.
US media outlets reported that Saunders, who is black and an outspoken supporter of LGBT rights, said her gesture was made in solidarity with "oppressed people".
But critics argue she has an unfair advantage over her rivals due to physical attributes locked into her body during her decades as a male.
Later in Tokyo, China's reigning Olympic champion Chen Long faces formidable Dane Viktor Axelsen in the men's badminton final.
Women's football is also reaching its closing stages with Megan Rapinoe's United States, the reigning world champions, taking on Canada while Australia play Sweden, the losing finalists at the 2016 Rio Olympics.
