The first call came in at around 01.30 BST on Sunday 3 April, reporting a vehicle fire in New Road, Stoke Gifford.
By 05.30am there were further reports, with up to 20 vehicles set alight in locations across Bradley Stoke, Little Stoke and Stoke Gifford.
At about 03.45am more vehicles were on fire in a car park at Rolls Royce, Filton. Around 20 vehicles there were damaged as the fire spread.
In a statement Avon & Somerset Police said:
“ Residents may have heard some of the vehicles’ fuel tanks exploding. Thankfully there have been no reports of injuries or damage to buildings.
“ We’re working closely with the fire and rescue service to respond to these incidents. Officers will be carrying out house-to-house enquiries and making a thorough investigation alongside Avon Fire & Rescue Service.
“ At this early stage the damage is making it difficult to identify vehicles in order to notify the owners. We’d like to hear from anyone who finds their own vehicle has been damaged, as well as anyone with information or dashcam, CCTV or other footage which could help our enquiries.
“If you can help, please call 101 and give the call handler the reference number Log 124 of Sunday 3 April, or complete our online appeals form.
“You can contact the independent charity Crimestoppers 100 per cent anonymously on 0800 555 111 or via their Anonymous Online Form.”