MINNEAPOLIS (WCCO) – Authorities in Cottage Grove are offering a reward for information after four fires have been intentionally set in the city in the span of about a week.

The Cottage Grove Police Department says the first incident happened at about 2 a.m. on Oct. 17, when a few portable bathrooms were set on fire.

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Authorities say on Oct. 21, a fire was set on the north side of Crestview Elementary School. Blue bins were set on fire, and authorities said it looked like burnt fireworks were in the bin.

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On Monday, a playground near Kingston Park suffered about $30,000 in damage after equipment was burned. On Tuesday, another fire was intentionally set near Grey Cloud Elementary School, which is also near Kingston Park.

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The Cottage Grove Public Safety Board is offering a $250 reward for information leading to an arrest. The incidents remain under investigation.