A major fire that gutted one West Cumbrian business and destroyed part of another was probably caused by waste paper being burned on the site, an investigation report has found.

At its height 60 firefighters tackled the inferno at Maryport's Glasson Industrial Estate on April 25, with flames reaching 100ft into the air.

The blaze was described by incident commander Adrian Holme as the biggest he had known in more than 20 years in the service.

It gutted a warehouse belonging to SIS Pitches and the neighbouring offices and workshop of Fearon Builders.

An interim investigation report into the fire has now been completed and fire chiefs have confirmed that the most probable cause was accidental, linked to a "controlled small fire" taking place on the site before the main blaze began.

A Cumbria Fire and Rescue Service spokesman said an SIS employee was burning waste paper in a brazier shortly before the inferno took hold.

It is believed that hot embers from the waste fire were blown onto rolls of polyester fabric stored on the site, which were used for artificial grass backing.

The spokesman added: "This hadn’t been noticed when the small fire had been checked and extinguished.

"A fire then started to burn unnoticed in the fabric rolls until the fire developed, became out of control and spread around the site."

Twelve fire engines from across the county attended the blaze, along with a specialist crew from Sellafield and a high-pressure pump from Kendal.

Businesses across the industrial estate and at Maryport Business Centre, on the opposite side of the railway line, were evacuated and the A596 from Maryport to Flimby and the Hutton Place/Irish Street entrance to the town were closed for almost 24 hours.

Trains and buses were disrupted while the fire was brought under control.

Grasslot Infant School closed early on Tuesday as pupils were upset by the incident and travel disruption became a concern for staff.

Seven hundred homes and businesses lost power after an electricity substation was damaged. It was restored to most customers within three hours, while 21 were left without power until generators were brought in on Wednesday evening.

People were advised to keep doors and windows closed because of the smoke.

SIS Pitches' factory, where its artificial turf is produced, was unaffected by the blaze.

An SIS Pitches spokesman declined to comment this week.

After the blaze, a spokesman said business was continuing as usual at the site.

Fearon Builders are still picking up the pieces from the fire, with its owners sifting through the charred remains of their premises to itemise losses for their insurers.

The firm temporarily relocated its offices to Workington after the fire but returned to the Maryport site, operating from a cabin, in recent weeks.

Terry Fearon, who owns the firm with brother Neil, said: "We are trying to go through and itemise everything for the insurance. It's finding time because we are trying to run the business as well.

"Business is slowly picking back up. We're trying to get everything so it's working fully again."