The Australian Open’s qualifying matches were delayed on Tuesday and practice temporarily suspended due to poor air quality as smoke from bushfires raging across the country blanketed Melbourne in a thick, grey haze.

The games were scheduled to start at 1000 am local time (2300 GMT) but did not get underway until about 1130 after Victoria state’s environment watchdog said air quality had plunged to “hazardous” levels overnight.

Tournament organisers said practice at Melbourne Park was also suspended in the morning.

“Conditions onsite are improving and are being constantly monitored,” Tennis Australia said in a statement.

“Further decisions will be made using onsite data and in close consultation with our medical team, the Bureau of Meteorology and scientists from EPA Victoria.”

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.

The Environment Protection Authority (EPA) warned residents on Tuesday to stay indoors, bring pets inside and keep windows closed.

A number of players who arrived in Melbourne ahead of the Grand Slam starting on Monday expressed surprise that organisers would allow qualifying to go ahead.

“Shocked to see that qualifying matches have started @AustralianOpen,” Luxembourg professional 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? #wherearethelimits?”

A number of top players, including former world number one Maria Sharapova, were scheduled to play at the warmup Kooyong Classic on Tuesday in Melbourne’s eastern suburbs where air quality was rated “very poor”.

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 the Bureau of Meteorology.

The pollution nonetheless prompted Racing Victoria (RV), the state’s governing body for thoroughbred racing, to scrap a race meeting in Melbourne’s western suburbs and for outdoor construction workers to down tools for the day.

The smoke haze was “unlikely to improve throughout the day making it unsuitable for racing”, RV tweeted.

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”.