Update: All lanes are now clear after an accident at I-41 south of Pilgrim Road near Monomonee Falls. 

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A crash has blocked all lanes of I-41 south at Pilgrim Road near Menomonee Falls. The back up is about three miles long.

Travelers are encouraged to use an alternate route.

CBS 58 has a crew at the scene who says it looks like the crash involves a motorcycle.

Stay with CBS 58 through this developing story.