Ceremonial jewellery belonging to the Lord Mayor of Bristol was stolen from a council building early on Monday morning (February 24).
Officers were called to a break-in at council premises near Brunel Lock around 5.30am.
Police said an unknown number of suspects forced their way into the property in Smeaton Road and stole two safes.
One of which contained the civic ceremonial jewellery.
Bristol's current Lord Mayor is Liberal Democrat councillor Jos Clark.
Bristol City Council has said it is still assessing the full extent of the damage caused during the break-in as well as exactly what was taken.
Avon and Somerset Police are asking anyone with information to contact them on 101 and quote the reference 5220044814.