UPDATE: Spontaneous combustion is believed to have provided the spark which ignited a large pile of garden mulch at the Bedford St Waste Facility.
Toowoomba Regional Councillor Nancy Sommerfield said Saturday night's blaze had erupted after the mulch, collected from residents' green waste bins, heated to ignition point.
"It just happens every now and then," Cr Sommerfield said.
Council staff remained at the scene until 2.45am on Sunday after extinguishing the blaze on the 50m by 10m heap.
The fire caused significant haze over the North Toowoomba area on Sunday.
"There has been no effect on services."
Council staff today continued to monitor mulch piles at the facility.
Mulch fire at Bedford St tip
EARLIER: Multiple fire crews and dozers attended the scene of a large mulch fire at Bedford St, Toowoomba last night.
Firefighters were called to the fire at around 10pm and arrived to find the mulch pile well alight.
While the fire posed no threat to homes in the area, it caused a significant smoke haze over the North Toowoomba community.
The blaze is expected to be a protracted incident continuing today.
The fire is now in the hands of Toowoomba Regional Council.