UPDATE: I-5 south slowly improving

A collision on southbound Interstate 5 at milepost 106, near Boulevard Road, has the left lane blocked. The backup had grown to four miles as of 1: 18 p.m.

The state Department of Transportation expects backups until about 2:15 p.m.

Farther north, heavy traffic is causing backups and possible delays on I-5 southbound from near the Pierce/King county line to near DuPont.