City of Ottumwa issued the following announcement on Sept. 9.
On Monday September 7, 2020, at approximately 7:07 p.m., the Ottumwa Fire Department responded to a fire at the Midwest Little League baseball field located in the 2000 Block of West 2nd. Officers from the Ottumwa Police Department also responded and began investigating the fire. On Tuesday, September 8, 2020, the Ottumwa Police Department charged a 13 year old female juvenile with Reckless Use of Fire, a Serious Misdemeanor. The juvenile was arrested and released to her parents.
Original source can be found here.