The M-26 at Silver River Bridge between Eagle Harbor and Copper Harbor closed on Saturday due to a collapse of the retaining wall.
Traffic will be detoured via a posted rout on US-41.
The closure is expected to last about 10 weeks.
The bridge has had single lane traffic since 2021 due to the deterioration of one of the historic stone retaining walls.
It was due to be closed on Tuesday as part of a $2.9 million project to be removed and replaced this summer.