MADISON (WKOW) -- The structure fire at a warehouse near Vondron Road remains under investigation as fire crews monitor the site for flare-ups, the Madison Fire Department said Wednesday morning.

On Tuesday around noon, reports of a possible explosion and smoke coming from a building prompted the response of firefighters, who saw white and gray smoke pushing from the eaves of the warehouse upon arrival. Thermal imaging showed firefighters that there were pallets of materials stacked from the floor to the ceiling in the 4Moto Engineers warehouse near 2334 Vondron Road.

Two engines, Engine Co. 8 and Engine Co. 14, began tackling the fire from two different sides, while conditions within the building deteriorated rapidly. Around 12:30 p.m., the fire was upgraded to a second alarm and more firefighters arrived on the scene to begin working on the rooftop. Madison Fire Chief Chris Carbon said the defensive firefight took several hours.

Around 4:30 p.m., firefighters were confident the main body of the fire was knocked down, but hot spots persisted. With support from the City of Madison Engineering, debris was removed and firefighters could continue cooling down smoldering items.

Fire crews remain to monitor the site on Wednesday.

At this time, the investigation into the cause of the fire continues. The Department of Criminal Investigation is assisting the Madison Fire Department Fire Investigation Team.