(CNN)Michigan's 911 emergency phone lines are working again after an hourslong outage early Friday, state police say.
A statewide 911 outage began around 2:30 a.m. ET, when the system was being updated. An unspecified technical issue knocked out the lines, state police said.
"We started seeing issues with the system right away (during the update)," Michigan State Police Lt. Derrick Carroll told CNN. "Once they saw that it was being shut down and they couldn't bring it back up, notifications (to the public) started to be made."
Some counties' service was restored over the next few hours. The outage was fixed statewide around 7:15 a.m., Carroll said.
Details about what caused the problem weren't immediately available.
During the outage, state police tweeted a list of alternative numbers for all counties' emergency dispatch centers and urged people to call those numbers if 911 wasn't working where they were.