Four days after 13 cars from a CN train derailed and exploded west of Edmonton, the main highway between Edmonton and Vancouver opened partially to traffic Wednesday.

Two westbound lanes of Highway 16, also known as the Yellowhead, are now serving traffic in both directions, though speed limits are reduced to 50 kilometres per hour.

Alberta Transportation engineers are assessing whether the eastbound lanes need repairs following the intense heat of the flames.

Thirteen rail cars containing crude oil and propane derailed and exploded Saturday. Firefighters have been burning off propane since then in an effort to get more than 100 residents back into their homes.

The evacuation order for residences near the derailment site was lifted yesterday afternoon.

The cause of the derailment is not yet known, but three investigators from the Transportation Safety Board are expected to complete their investigation by the end of today.