A fatal motorcycle crash on northbound I-5 at Mercer Street snarled the Thursday morning commute. 

The freeway was reduced to a single lane for hours as law enforcement investigated and cleared the scene. 

All lanes were reopened by 8:20 a.m. However, traffic backups remained for hours.

Trooper Rick Johnson says speed may have been a factor in the crash that killed the 52-year-old man from Arlington.No other vehicle appears to be involved. 

According to a Washington State Patrol memo, the motorcycle was traveling in the left lane when it veered to the left shoulder, striking the barrier. 

It's currently unknown if drugs or alcohol were involved.