JP Corry said on Sunday night nobody had been hurt following a major fire at their Crankill Road premises near Ballymena.
In a statement the firm said: “We can confirm there has been a fire at our JP Corry Ballymena (Robert Guy) branch.
“Fortunately nobody has been hurt and we are of course working with the local emergency services and will co-operate fully in their investigation.
“Our Pennybridge Industrial Estate branch will be open as usual tomorrow (Monday) to serve customers. We are extremely grateful to the local emergency services for all their work this evening.”
Firefighters were at the scene of the large blaze at the premises on the A26 Crankill Road.
A video on social media showed flames rising into the air from a building supply business close to Applegreen.
One eye-witness said: “This is one of the biggest fires I have ever seen. There are at least seven or eight fire appliances in attendance”.
The PSNI tweeted: ‘The A26 southbound carriageway Crankill Road, Ballymena is closed in both directions following a fire at premises in the area. Diversions in place at Drones Road roundabout and Fenagh Road.
‘Police assisting NIFRS with traffic management and motorists should avoid the area.’
Witnesses said damage would be severe.
Andrew Lennox was on the dual carriageway at around 6.30pm when he noticed smoke.
He told the Belfast Telegraph: “It is well developed. The fire is rightly up and has spread to the entire building.
“The fire service where on the scene not long after we had to stop at 6.30pm.”
The 29-year-old was coming from his sister’s house in Cloughmills to his Cullybackey home.
Six fire trucks, an aerial appliance and a water tanker attended the blaze.
Twenty-seven firefighters worked to extinguish the blaze.
Crews from Ballymena, Belfast, Dungiven, Antrim and Kilrea were sent to the scene.
On Sunday night, a Fire Service spokesperson said they had the blaze under control but were assessing the structural integrity of the building.
On Monday, the Fire Service tweeted: “The cause of the fire at JP Corry’s Ballymena has been confirmed as accidental. Over 30 Firefighters worked hard throughout the night to contain the fire to the two storey building. The incident has been dealt with & Firefighters left this scene at 9.40am this morning.”
Another statement issued by JP Corry on Monday said: “We would like to reiterate our enormous thanks to the local emergency services following last night’s fire at our JP Corry Robert Guy branch in Ballymena who worked throughout the night.
“Our priority is of course to make sure the site is safe and to conduct our analysis so that work can commence to get this historic site back up-and-running for our customers and colleagues.
“Customers can continue to collect materials from our other local JP Corry branch at Pennybridge Industrial Estate, or order materials for delivery as normal.
“All seven colleagues who worked at the site have been redeployed to our other local branches – and there is no risk to their roles.”
North Antrim MLA and TUV leader Jim Allister described the incident as a “big loss”.
North Antrim DUP MLA Mervyn Storey said he was “very sad” to hear of the fire at what he described as a “iconic landmark” on the A26.
He added: “It has been there before there was a dual carriageway and this is devastating for the owners and all those employed,” he said.
Mr Storey worked Agivey Bacon Plant (Lovell & Christmas Ulster Ltd) near the River Bann which was destroyed in a fire in 1999.
“I know what it is like to watch and see a livelihood burn in front of you. The consequences from this could be felt for many years.
“Hopefully something can be salvaged.”
The Mayor of Mid and East Antrim, Councillor Maureen Morrow, said her thoughts were with the staff and management at JP Corry .
Cllr Morrow said: “I am shocked and deeply saddened by the scale of devastation caused by the fire at JP Corry builders merchants’ yard.
“JP Corry is one of Northern Ireland’s leading building suppliers and to hear that one of their branches has been totally destroyed by a fire is absolutely devastating news. I would like to also extend my thoughts to the staff and management.
“I want to thank the Northern Ireland Fire and Rescue Service, whose quick actions and bravery prevented the fire spreading further.”
Sinn Féin councillor Cathal McLaughlin praised the prompt response of the emergency services.
Cllr McLaughlin said:“This is a well known and popular business in the area, supplying building contractors for many years, as Robert Guy’s and lately taken over by JP Corry Ltd.
“I would like to thank the emergency services for their prompt response this evening which saw the road closed and the area secured in a professional manner.
“We all hope JP Corry can get back up an running in this area in the near future.”
TUV councillor Timothy Gaston tweeted: ‘Sad to see fire devastating the JP Corry building on the A26’.