ST. CLOUD -- A large grass fire in St. Cloud is being investigated as a possible arson case.

St. Cloud Fire Marshal Mike Post says crews haven't been able to find a natural cause for Sunday's blaze which burned about 180 acres of land near the St. Cloud Prison.

"We believe it was human involvement that caused the fire. We are asking for the public's help and the Minnesota Arson Reward Project hotline at 1-800-723-2020, they can contact that. They can remain anonymous and rewards are up to $5,000 for the information leading to the identification of persons [involved]."

Crews battled the blaze for about six hours Sunday afternoon into the evening. One building owned by the Department of Corrections was destroyed in the fire. However, it wasn't being used for several years.

No injuries were reported.

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