CHEBOYGAN, Mich. (AP) — Explosive devices were found in boxes outside two phone stores in northern Michigan, the FBI said Friday, Sept. 17.

The devices were discovered Thursday in Cheboygan in the northern Lower Peninsula and Sault Ste. Marie in the Upper Peninsula, authorities said.

READ MORE: Michigan Reports 7,505 New COVID-19 Cases, 118 Deaths

The FBI urged the public to share information to help investigators find who’s responsible for the explosives. No one was injured.

“There were threatening notes addressed to Verizon and AT&T on the top of each box,” the FBI said. “The notes were signed either ‘HJ’ or ‘Handcuff Johnny.’ The letters ‘CMT’ were written on each box.”

READ MORE: Preserving Legacy, Sister’s Return To Revitalize Childhood Neighborhood, After Seeing Increase In Blight

The FBI and state police believe the explosives are related to letters found last month at communication towers across the Upper Peninsula. The letters made demands and claimed to be from the “Coalition for Moral Telecommunications.”

Anyone with information can call (800) 225-5324.

MORE NEWS: MDOT: Here's A List Of Weekend Construction In Metro Detroit

© 2021 Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.