UPDATE: 4:34 p.m.
Rockbridge Co., VA - VDOT is now reporting that only the left south shoulder is closed at mile marker 187.2 after a tractor trailer accident earlier Saturday.
At one point, southbound traffic was backed up nearly four miles.
Traffic appears to be moving at normal speeds, according to VDOT cameras available to ABC 13.
Rockbridge Co., VA- A tractor trailer accident is backing up traffic on I-81 south.
According to VDOT's web site, the accident is at mile marker 187.2.
The south left shoulder and south left lane are closed as of this writing.
Southbound traffic can be seen moving slowly on a VDOT traffic camera at mile marker 188.9.
Stay with ABC 13 News and wset.com for further updates.