1 arrested after bombs found outside northern Michigan cellphone stores

One person is in custody after bombs were found outside two cellphone stores in northern Michigan last week.

MORE: Explosives with notes threatening Verizon, AT&T found

The explosives were found inside USPS Priority Mail boxes sealed with black duct tape at stores in Sault Ste. Marie and Cheboygan on Thursday. The boxes had notes threatening Verizon and AT&T.

A suspect was arrested Monday night. Authorities said they couldn't provide more details because the person has not been arraigned.

The FBI and Michigan State Police believe the explosives are related to a series of letters discovered at telecommunications tower sites in the UP last month that made specific demands to the companies.

The incident remains under investigation. Anyone with information is asked to contact the FBI at 1-800-CALL-FBI or tips.fbi.gov.