New Holstein and Kiel police investigated several loud booms heard in New Holstein on Sunday night, March 1 just after 9 p.m.
One boom was heard followed by several others. Multiple calls went to 911 from people throughout the community, and people several miles north of the city heard them as well. Some callers said smoke was seen on the north side of the city.
As of 10 p.m. there was no report as to the cause of the booms. Callers to 911 and people on social media offered theories ranging from gunshots to fireworks to "frost quakes" caused by the day's high temperatures well into the 40s.