A row of terraced houses caught fire close to one of the huge loyalist bonfires lit in the North to usher in the main date of the Orange Order's parading season.
Two homes adjacent to the Hopewell Square bonfire in Belfast's Shankill Road were gutted when a blaze broke out on the roofs of the terrace at around 1am. At least one other house was damaged.
It is suspected that hot bonfire embers were blown on to the roofs by the wind.
Almost 600 loyal order parades will take place across the North today to mark the Twelfth of July.
The total number of call-outs received by the Northern Ireland Fire & Rescue Service (NIFRS) overnight was up on last year.
Of the 123 calls between 9pm and 1am, 42 were bonfire-related. At 16 of those callouts, firefighters had to actively intervene.
As well as Belfast, fire crews attended bonfire-related incidents in Bangor, Coleraine, Banbridge, Rathfriland, Dungannon, Derry City, Portadown, Ballyhalbert and Limavady.
The NIFRS said there were no reports of any crews being attacked.
The lighting of the towering bonfires, most built with stacks of wooden pallets, drew thousands of onlookers, but the structures were again the source of controversy, despite the efforts of organisers to improve their image.
To their defenders they make for a family-friendly, spectacular celebration of loyalist/Protestant culture; to their detractors they are potentially dangerous, environmentally damaging, magnets for anti-social behaviour and alienating to nationalists.
There were complaints of the burning of Sinn Féin election posters made for May's Stormont Assembly poll as well as the use of toxic tyres.
In recent years, bonfire builders have faced criticism after items linked to the nationalist/republican tradition - such as Irish flags and posters, and effigies of high-profile politicians - were placed on top of some of the fires and torched.
Last year, homes near Chobham Street in east Belfast had to be evacuated over fears that the giant nearby bonfire could topple on to property.