West Midlands Fire Service has confirmed that Willenhall Road near to the disused building on Lower Horseley Fields remains shut.
Bus services 82 and 529 are diverted in both directions via Deans Road and Wednesfield Road.
At its height 28 fire engines and more than 100 firefighters were on the scene of the blaze which started at around 9pm and engulfed multiple factory units.
Crews also used a thermal imaging drone to identify hotspots in the blaze, which at one stage covered a fifth of a square kilometre.
The railway through Wolverhampton has reopened after it was closed due to the major fire nearby.
Due to the risk of a factory wall collapsing, the railway was closed and train journeys disrupted.
National Rail said the railway line had safely reopened at about 6:45am.
CrossCountry, Avanti and West Midlands Railway were among the operators affected.
A spokesman for Network Rail said: "We're sorry to passengers impacted by the fire next to the railway."
Investigations are still ongoing to what caused the fire but explosions were heard and smoke could be seen from 15 miles away.