Recently crowned Pan American Games middleweight champion Naomi Graham narrowly won her first bout here at the International Boxing Association (AIBA) Women's World Championships to reach the quarter-finals.
The American finished with a bronze medal at last year's World Championships in New Delhi, but only just triumphed against Atheyna Bylon of Panama, edging past her opponent 3-2.
Graham will battle Canada's Tammara Thibeault in the quarter-final, with the division's eighth seed recording a unanimous victory over Sarah Scheurich of Germany.
Nouchka Fontijn of the Netherlands also enjoyed a unanimous decision against Akerke Bakhytzhan of Kazakhstan.
Top seed Fontijn achieved silver at both the Rio 2016 Olympic Games and last year's World Championships.
Her next opponent will be Zheng Lu of China, who overcame Erika Pachito of Ecuador 5-0.
Competition also took place in the featherweight division, with top seed Lin Yu-Ting of Chinese Taipei continuing her impressive title defence with a unanimous win against Poland's Kinga Szlachcic.
Nilawan Techasuep of Thailand got past Amanda Millere of Latvia by the same result to set up a quarter-final clash with Lin.
🥊 RESULT 🥊— IABA (@IABABOXING) October 8, 2019
Its so close for Ceire Smith at @ulanude2019 but she bows out on a split decision (3-2) to the #1 Seed from 🇰🇵
A tough loss for the Cavan flyweight but great experience gained for the road ahead.
Hard Luck Ceire!🇮🇪#TeamIreland #RoadToTokyo #CantSeeCantBe pic.twitter.com/geIhuViC1c
Dutch fourth seed Jemyma Betrian survived a scare to beat Aizhan Khojabekova of Kazakhstan, but is scheduled to face home favourite Liudmila Vorontsova next.
The Russian boxer stunned two-time European silver medallist Michaela Walsh of Ireland 4-1.
In the flyweight division, North Korean top seed and defending champion Pang Chol-mi was underwhelming in her tie against Ireland's Rose Smith, defeating her 3-2.
She meets Tsukimi Namiki in the quarter-final, with the Japanese boxer securing a unanimous win against Nina Radovanovic of Serbia.
Vietnam's Thi Tam Nguyen, who lost to Pang in last year's final, was another unanimous victor, this time against Allantsetseg Lutsaikhan of Mongolia.
The sixth seed's next opponent will be Russia's Liliya Aetbaeva, who beat Grazieli Jesus De Sousa of Brazil 4-1.
The quarter-finals are on Thursday (October 10).