Investigators are trying to determine what sparked a fatal house fire in Waterloo late Saturday (Dec. 30, 2017).

Waterloo Fire Rescue officials said crews found Robert Smiley, 63, in the basement of the home after a neighbor reported the blaze around 11:15 p.m. Smiley was rushed to a nearby hospital, where he was pronounced dead.

According to firefighters, Smiley owned the house and lived there alone.

Fire officials said the blaze started in the basement of the home, but the cause remains under investigation.

Sub-zero temperatures initially hampered firefighters when they first arrived at the scene. Officials said the hydrant closest to the burning house was frozen, so they had to extend their hoses to another hydrant further away.