Police have launched an investigation into a suspicious fire in O'Connor overnight.

At about 1.30am ACT Fire and Rescue responded to reports of a structure fire on Berrigan Crescent.

Firefighters arrived to find fire in the upper levels of the building with fire spreading into the roof space.

The building which was unoccupied at the time sustained damage, and there were no reports of injuries.

Following initial investigation, the cause of the fire has been deemed suspicious.

This is the second fire to occur at the apartment complex in the last 6 months with a signifcant fire damging the property in August 2023.

Anyone with information about this incident is urged to contact Crime Stoppers on 1800 333 000 or via www.crimestoppers.com.au.

Please quote reference 7648897.