An international traveller, who absconded from a quarantine hotel in Adelaide, spent several hours in the city, sparking a COVID-19 scare and a major investigation.

However, police say the man, who left the hotel about 10pm on Thursday, has tested negative for the virus and there is no threat to the wider community.

He had arrived in Adelaide on August 3 and was immediately taken to the Grand Chancellor Hotel to complete two weeks in mandatory isolation.

He tested negative for COVID-19 on days one, five and nine.

Police said it had been determined the man had been in the Adelaide CBD for about eight hours and returned voluntarily to the hotel about 6am on Friday.

Police Commissioner Grant Stevens said it was disappointing the hotel breach had occurred despite robust security arrangements

“There have been about 22,000 guests in our medi-hotel program throughout the COVID-19 pandemic, and this is the first time we have seen such a breach,” he said.

“I would like to reiterate that there is no known risk to the community, and South Australians should not be alarmed.”

Mr Stevens said a senior officer had been assigned to investigate the breach and a report was expected in the coming days.

“Action against this man regarding the breach of quarantine conditions will be addressed as a part of the investigation,” he said.

“We will continue to work to maintain the high standard of security in our medi-hotels and will implement any identified changes to restrict future similar breaches of security.”

-AAP