At its height, 75 crews tackled the fire on Walsall Road
Firefighters have been tackling a "large fire" at a recycling plant in Birmingham.
At its height, 75 firefighters tackled 500 tonnes of paper alight at Premier Waste on Walsall Road, Perry Barr. West Midlands Fire Service was called at about 02:50 BST.
The A34 was closed in both directions but has since reopened.
The service said crews had also dealt with a blaze at another recycling firm in Wolverhampton on Monday morning.
It saw up to 60 firefighters called to Lower Walsall Street at about 02:00 BST, a spokesperson said.
The causes of the fires are not yet known and both are being investigated, he added.
People living in the Perry Barr area have been urged to keep windows and doors shut.
A service spokesperson said the fire had been contained, but was not yet completely out. About 45 firefighters remain on site, he added.
Crews have been searching the building for "pockets" of fire that might have sprung up.
Station Commander Dave Hilton said crews were expected to stay on site for the rest of the day.
A spokesman from Premier Waste said the firm was open for business "with limited resource". No one had been on site overnight at the factory, he added.
The service said the fire was about "half the size" of a blaze caused by a Chinese lantern at a recycling factory in Smethwick in June, the 15th fire at a waste recycling site in the West Midlands this year.
Simon Shilton, area commander from the fire service, said the recycling plant fires risk becoming "a real drain on our resources".
Of the Perry Barr incident, Mr Shilton said: "It created a hugely intense fire in one building, fortunately we were able to contain it.
"At some stages the external parts of the building were glowing red, and that makes it even more challenging."
Another fire, caused by spontaneous combustion, broke out at Lawrence Recycling in Kidderminster, Worcestershire in June. Part of the site is currently being demolished in order to fully extinguish the burning.
The Recycling Association, which represents 65 recycling businesses across the UK, said only a few insurance companies were willing to cover recycling firms, which meant high premiums.
"After the summer, we will be linking our insurance premiums to health and safety performances," said Simon Ellins from the association.
"Each facility will be fully audited, putting into place all health and safety procedures.
"Then it is in the owner's financial interest to keep on top on health and safety, because failing to do that would hit them in the pocket."