HARRISONBURG, Va. -

Drivers should expect delays on Interstate 81 near Harrisonburg.

A tractor-trailer accident has closed both directions near mile marker 243. The accident knocked down power lines.

The Virginia Department of Transportation asks drivers to consider an alternate route.

There is a three-mile backup on I-81 North.

It could be several hours before I-81 re-opens, according to VDOT.

The tractor-trailer driver was not hurt.