A player collapsed in a coughing fit and was forced to retire from Australian Open qualifying on Tuesday after organisers ploughed ahead with matches despite bushfire smoke plunging Melbourne's air quality to "hazardous" levels overnight.
Slovenia's Dalila Jakupovic was leading 6-4 5-6 in her qualifier against Stefanie Vogele at Melbourne Park when she slumped to her knees at the back of the blue hardcourt suffering apparent breathing difficulties.
Her retirement came only hours after tournament director Craig Tiley defended the decision to proceed with qualifiers after they were initially delayed due to poor air quality.
"Today when we got up the smoke haze was significant so we made the decision to suspend practice and, as a result, to start the qualifying matches an hour later than was originally scheduled,” Tiley told reporters before Jakupovic's retirement.
"During the period of when we suspended practice and restarted the matches there was an improvement in the conditions."
Governing body Tennis Australia had earlier said in a statement that "conditions onsite (were) improving" and were being "constantly monitored" after Victoria state's environment watchdog warned residents to stay indoors, bring pets inside and keep windows closed.
Twenty-eight people have been killed and thousands made homeless in recent months as huge fires across the country have scorched through 11.2 million hectares (27.7 million acres), nearly half the area of the United Kingdom.
The bushfires have affected a number of elite sporting competitions involving soccer, rugby league and cricket, and poor air conditions have raised fears for players' health at tennis's first Grand Slam of the year.
Players who have arrived in Melbourne for the tournament woke to a pea-soup haze blanketing the city on Tuesday.
"Shocked to see that qualifying matches have started," Luxembourg's Mandy Minella, who is competing as a qualifier, tweeted. "What about the health of all the people that have to work out there, especially the ballkids?"
Victoria's Chief Health Officer Brett Sutton told local media the air quality in Melbourne had been the "worst in the world" overnight.
Other top players, including former world number one Maria Sharapova, were preparing for the year's first Grand Slam at the warmup Kooyong Classic on Tuesday in Melbourne's eastern suburbs where air quality was rated "very poor".
Russian Sharapova's match with Germany's Laura Siegemund was called off with Siegemend leading 7-6 5-5 after both players complained to the chair umpire.
"After two and a half hours that was the right call for me. I think both of us felt it," Sharapova told reporters.
"This is obviously maybe more extreme than some of the other conditions we’ve had but other than you just have to be ready."
A tournament spokeswoman told Reuters the players had agreed to play and organisers deemed conditions safe for matches to go ahead after receiving advice from authorities.
Racing Victoria (RV), the state's governing body for thoroughbred racing, decided to scrap a meeting in Melbourne's western suburbs as the smoke haze made conditions unsuitable for racing.
The EPA's air quality controller Jason Choi told state radio the smoke would likely linger until Wednesday when afternoon showers were forecast.
Australian Open men's champion Novak Djokovic expressed concern earlier this month that bushfire smoke might cause some health problems for players.
Tournament organisers said last week that play would be confined to Melbourne Park's three roofed stadiums and eight indoor courts in the "unlikely case of extreme smoke conditions".