The northbound and southbound lanes of the 18 Mile Stretch were shut down Thursday afternoon because of a serious traffic accident.
There are unconfirmed reports that a state Department of Corrections inmate working on a road crew was struck by a vehicle. At least one person was taken to a mainland hospital by air ambulance.
The Monroe County Sheriff's Office said the crash with injuries happened at mile marker 116, which is on the Miami-Dade County side of the highway. The 18 Mile Stretch is part of U.S. 1. It leads from the mainland in Florida City to Key Largo.
The wreck happened around 2 p.m.
Northbound traffic was cleared around 3 p.m.