The spark that ignited the Marshall Fire remains a mystery

• The next phase will take weeks or months as experts analyze evidence.
• Once complete, the district attorney will determine whether criminal charges are warranted.
• The sheriff's office says it won't release any more information until then.

What to watch: Two potential causes remain the focus of the investigation.

• Authorities executed a search warrant on the property of a Christian sect known as Twelve Tribes after reports emerged of a controlled fire on the property days earlier and another the morning of the Marshall Fire.
• Investigators also are looking at whether underground coal mines on the Marshall Mesa dating back to 1863 would have provided the heat to ignite the fire.

Flashback: The wind-fueled fire started Dec. 30 and quickly consumed entire neighborhoods, destroying more than 1,000 homes and killing two people.

• The initial cause was reported by officials as downed power lines, but that was later recanted.

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