DUPONT, Wash. (AP) — Traffic officials have re-opened all lanes of southbound Interstate 5 south of Tacoma following Monday's deadly train derailment.

The Washington State Department of Transportation says crews completed their work late Wednesday and there are no remaining highway closures through the crash site n ear DuPont.

The train derailment Monday that killed three people had spilled cars onto the highway and closed the southbound lanes of the state's main north-south arterial during the busy holiday travel period.

Federal investigators trying to determine the cause of the wreck want to know why the train was travelling more than double the posted speed limit when it went off the tracks.