Minn. Stat. § 88.15
Subd. 1. Extinguishment.
Any forest officer, conservation officer, or other peace officer who finds that any person has left a campfire burning shall take measures to extinguish the fire and take action against the person or persons responsible for leaving the campfire burning.
Subd. 2. Not to be left burning.
Every person who starts or maintains a campfire shall:
(4) before leaving the site, completely extinguish the campfire.
For the purposes of this section, "maintains" means tending or adding substantial fuel to a campfire with the effect of extending the life of the campfire.