ACT Policing previously believed the group arrived and left the ACT on January 26.

Following investigations into the breach ACT Policing now understands the tour group travelled to the ACT on January 23 and camped in Corin Forest until Australia Day.

An ACT Policing spokesperson said enquiries relating to other places the group may have visited are continuing.

The alarm was raised after the group was asked for their postcode at the Parliament House gift store following a tour of the building.

Parliament House underwent deep cleaning following reports of the travel breach.

The group travelled back to Sydney on Tuesday. It is not known how many people were in the tour group.

An ACT Health spokesperson said the risk of the incident was very low and contact tracing was not required.

"The situation with regards to community transmission in the Greater Sydney area has improved significantly over the past fortnight," the spokesperson said.

"The most-recent exposure location in Sydney of significant concern is from January 15, 2021 ... the risk of exposure to an undiagnosed case of COVID-19 from Sydney to the ACT community and staff within Parliament House is very low."

ACT Policing said they are still investigating the incident and fines or official cautions may be issued by police.

Those found flouting ACT's COVID-19 restrictions can face fines of up to $8000.

Health Minister Rachel Stephen-Smith said on Wednesday that ACT Health took COVID-19 breaches seriously.

"Public health directions are there for a very good reason," she said.

"When people are asked not to travel to a particular area or they are asked to quarantine, or required to do so by a public health direction, we expect people to abide by that," Ms Stephen-Smith said.

Travel between the Cumberland local government area and the ACT was banned until 3pm on Friday.

People in ACT who visited the Cumberland area were able to leave quarantine on Friday following changes to travel restrictions.