The man in his 60s received the result "consistent with an historic infection of COVID-19" on his last day in quarantine.

"The test result reflects prolonged shedding of virus fragments. This is known to happen intermittently for up to several months after a person is no longer infectious," ACT Health said in a statement.

"We are confident that the individual is not infectious and poses no risk to the community. As a precaution, however, further tests will be conducted today."

The man will remain in quarantine.

As the case was previously reported while the man was overseas it will not be counted in the ACT's case numbers.

Meanwhile, 166 returned travellers have been released from hotel quarantine.

One passenger returned a "low positive" result for COVID-19 on Monday but was also released from quarantine as authorities say she posed no risk to the community.

ACT Health authorities on Monday said they were confident the woman, who is in her 30s, returned a positive reading during hotel quarantine exit testing because of an old an inactive infection.

There have been 118 cases of COVID-19 in the ACT. Three people have died and 115 have recovered.