TUMWATER, Wash. -- A semi tractor-trailer loaded with 20 tons of drywall rolled over during a crash on northbound Interstate 5 in Tumwater, spilling its load and halting traffic.

The Department of Transportation said the crash happened shortly after 2 a.m.

The freeway was shut down at the site until 9 a.m., when one lane reopened to traffic. Traffic was backed up for eight miles.

DOT crews and the city of Olympia are cleaning up the 40,000 pounds of drywall that spilled across all three lanes.

Traffic is being routed past the scene using exit 103 at Deschutes Parkway.

Drivers are advised to take alternate routes.