Fire damage to the front doors of Old Parliament House in Canberra was “tragic” and potentially irreparable, Museum of Australian Democracy director Daryl Karp says.

The fire broke out amid a protest at the entrance to the historic building on Thursday, causing extensive damage to the doors and portico.

“We have a team of conservators standing by to come in and have a look and see what can be done because we are a museum, we love to be open 364 days of the year,” Ms Karp told the ABC.

“To actually be closed and to be closed because of violent protests is really tragic.”

Protesters had been outside the building for more than a week and started a traditional smoking ceremony.

A previous fire was started by protesters near the building on December 21.

• Related: Fire breaks out at Old Parliament House

Protesters had been outside the building for more than a week and started a traditional smoking ceremony.

A previous fire was started by protesters near the building on December 21.

Ms Karp said further examination was needed to determine if damaged parts of the heritage-listed building could be fixed.

She said the doors were “pretty damaged” and the portico had been “really burnt out”.

“The portico was built specifically for the Queen’s visit in the 50s and so it has substantial significance, as do the doors which are from 1927,” she said.

“It’s unclear whether we can restore the doors or not. Obviously they are pretty significant collection items and that’s a really big one for us.”

Ms Karp said the lower gallery floors were original 1927 lino.

“It’s got a lot of soot and a lot of water on it so we will need to check it is still okay.

Social media footage shows police dragging protesters away from the front steps of the building and a large fire burning at the doors.

Aboriginal Tent Embassy activists distanced themselves from the protest, saying a smoking ceremony that took place did not have knowledge or consent from the Embassy Council.

Police confirmed officials had agreed a small smoking ceremony could take place as part of a peaceful protest but said it got “a little bit out of hand”.

Greens senator Lidia Thorpe retweeted footage of the fire and wrote “Seems like the colonial system is burning down. Happy New Year everyone”. The tweet has since been deleted.

Deputy Nationals leader David Littleproud said her reaction was “disgraceful”.

“For politicians to sit there and encourage this, it is not responsible, it is disgraceful, and they should consider their position in the Australian parliament,” he said.

Mr Littleproud called for charges to be laid over the fire.

“No matter your race, no matter your religion, no matter your beliefs … no-one has the right to vandalise, particularly a symbol of our democracy, a symbol that 100,000 Australians have lost their lives defending,” he said.

“This is something police have to ensure charges are laid if appropriate.”

ACT Policing announced on Thursday it would launch an investigation into the blaze, noting while there were no injuries there was “extensive water damage” to the building’s interior.

-AAP