All lanes of southbound I-5 in Olympia reopened around 6 a.m. after a fatality investigation on Tuesday. 

The incident occurred at milepost 104.7 near Capitol Boulevard SE just before 3 a.m., according to the Washington State Department of Transportation. 

Drivers heading south on I-5 to US 101 or Portland were asked to delay their trips. 

There was a four-mile traffic backup by 6:15 a.m.