Police are treating as arson a ferocious fire at a paper mill which caused tens of thousands of pounds of damage to stock.

It took firefighters more than 14 hours to get the blaze under control.

When fire crews arrived at Garnett's Paper Mill in Wharfeside, Otley, the fire, which was fuelled by paper bales being stored outside the mill, was threatening to spread.

Crews from Rawdon, Otley and Cookridge attended the incident, which started at the back of the mill on a tip area, at 7.40pm on Tuesday.

They were replaced by crews from Stanningley and Keighley at 11.30pm, who stayed all night to stop the fire spreading.

Firefighters were still at the scene yesterday morning, using a ground monitor and a jet to make the area safe.

Garnett's personnel manager David Dickenson said the most likely cause of the fire was children messing around.

"We had reports from the security officer on Monday that he'd seen children coming into the tip," he said. "We are concerned about children coming on to the site and the danger they are creating for themselves and others, because bales do fall."

Mr Dickenson said the burned paper had been waste paper which had substantial value because it could have been recycled and reused.

He estimated around 135 tonnes of sheeted and reeled material had been destroyed.

"There's been no effect on the business and no person was in danger due to the fire but that's simply because of where it was," he said.

"It has different value depending on the quality of the material but there will have been several thousand pounds of damage caused here."

Mike Popple, watch manager at Leeds Fire Station, said the fire had been large, but there had never been any danger of it spreading to the building 15 meters away.

He said: "We controlled the fire by surrounding it with jets. The paper was mounted up like straw bales and so we had to use a fork-lift-truck to take them apart, one by one, to check that they were not smouldering."

The mill has hired a JCB to remove the rubbish and after the bales of paper have cooled down they will be sent to a landfill site.

Police in Otley are appealing for information.

A police spokesman said: "Inquiries into the cause of the fire are ongoing and any witnesses or anyone with any information is asked to call PC Joe Westerman at Otley neighbourhood policing team on (01943) 858035."

e-mail: ali.davies@bradford.newsquest.co.uk