EMBED >More News Videos ATF agents were searching an apartment in Raleigh on Tuesday evening.

RALEIGH, North Carolina (WTVD) -- Sources close to the investigation tell ABC11 that federal agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives were searching an apartment Tuesday evening at an apartment complex in connection with the massive downtown Raleigh fire.ABC 11 has obtained exclusive video of ATF agents at the Windsor Falls apartment complex in the 1500 block of Sunbow Falls Lane in Raleigh.Sources said the agents were searching a particular unit at the apartment complex but did not specify which unit was being searched.At least a half dozen agents were on site.The ATF called in its National Response Team on Friday to help with the investigation into the cause of the fire.The ATF uses extra resources to help with investigations into large fires, such as the one on West Jones Street. The fire is Raleigh's worst since the 1920s.The flames destroyed the Metropolitan Apartments, which were under construction. The fire damaged several neighboring buildings as well displacing many businesses and residents.