8:20 a.m. update: A wreck that shut down all southbound lanes on Interstate 35 North near Wells Branch Parkway has been moved to the right shoulder of the roadway, but traffic remains tied up past FM 1431, near Round Rock Premium Outlets. A second wreck in the same area blocked the left lane but was also moved to the right shoulder.
Earlier: A wreck involving multiple vehicles Friday has blocked all southbound lanes of Interstate 35 North near Wells Branch Parkway in northern Travis County.
As of 7:30 a.m., a tow truck was at the scene as the wreck was being cleared.
Heavy delays are expected for some time and commuters are being urged by authorities to seek alternate routes, such as Texas 130 or MoPac Boulevard (Loop 1).
Traffic was backed up as far north as the Texas 45 toll road.
This is a developing story, check back for details.