RIO DE JANEIRO: Yulia Efimova of Russia was greeted by some booing after winning her heat in the 100-meter breaststroke preliminaries.
The reigning world champion was allowed to compete at the Rio Games after serving a 16-month suspension for doping and again testing positive this year for the now-banned substance meldonium.
The IOC initially banned Efimova, along with six other Russian swimmers who either had positive tests on their record or were named in an investigation of the massive, state-sanctioned doping.
Efimova had the second-fastest time of 1 minute, 5.79 seconds. Lilly King of the U.S. was the leading qualifier in 1:05.78.
Also advancing to the semifinals on Sunday night was Katie Meili of the U.S., world record holder Ruta Meilutyte of Lithuania and Shi Jinglin of China.
Efimova also is expected to swim in the 200 breast and possibly the 4x100 medley relay.