I've had to skim to catch up so forgive me if this has already been answered.
This article has comments from the neighbors about the fire. However, there have been reports from other neighbors who did not see or smell anything.
Mackenzie Lueck disappearance: Police spotted digging holes at Utah home after neighbors report recent fire, ‘strong stench’
Police combing a Salt Lake City home for clues on the whereabouts of missing University of Utah student Mackenzie Lueck were spotted digging holes into its backyard early this morning following claims from neighbors that its owner recently was burning something that let off a
“strong stench.”
[...]
Neighbors who spoke to the newspaper say they recently saw the homeowner burning something in his backyard and
smoke from the fire was traveling into their windows.
[...]
“It definitely assaulted your nose,” Joseph Peterson, who lives one block west of the home, told the Salt Lake Tribune, describing how he got home one night from work only to smell a “strong stench” in the air.
[...]