The Koochiching County Sheriff’s Office has confirmed that the loud boom and ground tremors reported by northern county residents yesterday morning were caused by a controlled blast at a quarry just north of Fort Frances, Ontario.

The blast occurred around 9:00 a.m. Tuesday, carried out by a construction company working at the site. Emergency Management officials have since been in contact with the company and will now receive advance notice before any additional quarry blasts take place.

County residents will be notified ahead of future scheduled blasts to prevent confusion or alarm.