Officials from the Bureau of Alcohol, Tobacco, Firearms and Explosives are joining the investigation into the fire at the Mizpah Hotel in Reno.
An ATF Senior Special Agent said a national response team of veteran agents will be assisting local agencies. A Reno Fire Department official said the investigation involves a fairly large crime scene.
ATF said the first priority is to make the hotel safe for officials to work in. The Fire Department said some areas need shored up.
Authorities will be looking for evidence and investigating what caused the fire.
A resident of the Mizpah Hotel has said a mattress was set on fire inside. Police arrested Valerie Moore, 47, on suspicion of first degree arson and multiple counts of murder.