The fire broke out about about 3pm on Wednesday in units in the Park Street area of Kidderminster, leading to fireballs and think black smoke rising high into the sky.
More than 100 firefighters and 20 appliances tackled the blaze after several explosions were heard at Betts Metals.
Despite the fire's severity no-one was injured, although a number of residents were evacuated, with a rest centre opened up nearby.
19 schools were also closed on Thursday due to lingering smoke in the town, with people told to keep doors and windows closed.
Shropshire Fire and Rescue Service sent an incident support unit and operations office to the scene to help the Hereford and Worcester Fire Service.
In the early hours of Thursday fire crews from Ludlow and Tweedale were also sent to the scene to take over from appliances that had been on site for several hours.
Witnesses have recalled running for their lives to escape the blaze.
Aron Jacques, the 32-year-old manager of ATS Euromaster Kidderminster, said his building was shaken by several explosions.
He said: "It is all a bit of blur about what happened. There was loads of smoke and the building we were in which was next door began shaking.
"There were flames coming through the roof next door and the three of us just ran for our lives to the Spa shop down the street.
"I knew there was dangerous stuff in the building where the explosions were occurring and we just ran for our lives."
Lisa Pryce, aged 53, who lives nearby, said: "I am just relieved that we still have our house.
"I was out walking the dog at Dunley and we could see the smoke from ten miles away.
"A friend messaged me and asked if I knew what was going on down my street.
"He sent me a picture of the smoke.
"It is only because the wind was in the opposite direction that the fire did not spread to our side and take out the houses along Park Street."
Speaking on Thursday, corporate communications manager at Hereford & Worcester Fire and Rescue Service, Richard Prime, said the incident had been scaled down.
He said: "We have four fire engines on site plus an aerial ladder platform and incident command unit.
"The fire investigation remains ongoing. Efforts are being made to reduce the cordon so people can go back to their homes and businesses.
"There are still one or two pockets of fire, it's not fully out yet."