About 100 firefighters and 20 fire vehicles were in attendance at the peak of the fire in Kelvin Way on Friday evening, and nearby residents have been warned to keep their doors and windows closed.
A fire service drone patrolled the skies to support decision-making on the ground.
As of about 5pm on Friday the fire was under control, said West Midlands Fire Service. A statement said: "Less than three hours after this huge fire was first reported to us, we now have it surrounded and under control.
"Staff at the recycling company have been using their own machinery to help our crews, by creating fire breaks and moving material around the site.
"We've had a high volume water pumping unit at the scene, and water from a nearby canal has been used on the fire.
"People who live or work nearby are still asked to keep doors and windows closed if their home or workplace is affected by the smoke."
The fire took hold at a recycling centre and involves large bales of cardboard, near to a number of industrial units. Current estimates are that the fire involves 300 tonnes of compacted, baled cardboard.
An eyewitness who wanted to remain anonymous said: "We saw lots of smoke from the West Brom direction as we were driving past. There were huge plumes covering half the sky.
"As we got closer, we saw more and more smoke and there were emergency services going past. Everyone was staring. We assumed it was a tyre factory or something similar, given the direction it was in.
"We just hope everyone got out."
The fallout from the fire could be seen from as far afield as central Birmingham, Worcester and even parts of Telford.
Surrounding roads were badly congested and a number of National Express services were delayed.
It could also affect the nearby M5 at Junctions 1 and 2, with motorists reporting black smoke billowing overhead.
A spokesperson for West Midlands Fire Service said: "Shortly after 2.15pm on Friday 19 August, we started to receive several 999 calls reporting a fire in Kelvin Way, West Bromwich.
"Eight fire engines and some 50 firefighters responded, with the first of our crews arriving on scene five minutes after being mobilised.
"Resources were soon increased to 12 fire engines and 60 firefighters.
"At the time of this update (3.10pm on August 19), people in the local area are being asked to keep doors and windows closed as a precaution.
"Smoke has the potential to affect the nearby M5 motorway. The fire involves large bales of cardboard, near to a number of industrial units. Local road closures are in place."
West Midlands Ambulance Service also attended, and tweeted: "We're in attendance at Kelvin Way in West Bromwich supporting @WestMidsFire colleagues who are tackling a fire.
"If you’re in the local area please keep windows and door shut to avoid breathing in smoke."
The ambulance service later said: "We were called at 2.35pm to reports of a fire on Kelvin Way, West Bromwich. We currently have a paramedic officer in attendance standing by to support the fire services. There are currently no reported patients.”
The Twitter account for West Midlands Roads said: "This route is closed due to a significant fire that has occurred at a nearby industrial estate.
"This is causing heavy congestion in the surrounding areas. Avoid this route and consider using alternative roads."
They advise that there are 20 minute traffic delays in the area.