An Australian Open testing blitz has revealed no new coronavirus cases, organisers said Friday, putting preparations for the Grand Slam tournament back on track after a Covid scare.

Preparations for the year's opening tennis Grand Slam were thrown into disarray when a worker at one of the designated tournament hotels became infected with the virus.

Some 507 players and officials were ordered to be tested and isolate until they received their result, with six warm-up tournaments suspended on Thursday.

But they were all cleared on Friday as the tournaments resumed at Melbourne Park.

"All tests conducted on AO (Australian Open) quarantine participants yesterday have returned negative results," said a tweet on the tournament's official Twitter account.

Victoria state had gone 28 days without a locally acquired infection before the latest case, which prompted a tightening of restrictions around wearing masks, with authorities wary of coronavirus cases after Melbourne spent four months in lockdown until late October.

More than 1,000 players, coaches and officials flew into largely virus-free Australia last month, sparking debate over whether the tournament should be held during a coronavirus pandemic.

While most players were allowed out to train for five-hour blocks during their lockdown, 72 were confined to their hotel rooms 24 hours a day after eight positive Covid-19 cases were detected on the charter flights.

Despite the latest scare, Australian Open boss Craig Tiley said he was confident fans would still be able to attend matches this week and at the Australian Open, which starts on Monday.

"Spectators will continue to be allowed in the site, and we are still selling tickets," he said.

"The site will be an extremely safe place. There's health checks, contact tracing set up, divided into zones, physical distancing."

Daily crowds of between 25,000 and 30,000 are allowed at the Australian Open, equating to about half the attendance of last year.

Play began an hour early with WTA clashes reduced to two sets and a super tiebreaker instead of their usual three sets to ease the backlog after Thursday's suspension.