FIREFIGHTERS spent six-and-a-half hours dousing a huge "chip pan fire’’ involving 10,000 litre oil tanks at a Church refinery.

The blaze is believed to have been caused by overheating insulation on one of the vast, 20-foot- high containers, which then spread to a second tank.

The Prosper De Mulder (PDM) refinery, formerly Ashworth Products, on Bridge Street, collects and processes used vegetable oils and animal fats into biofuel.

Two pumps from Hyndburn attended the incident between 6am and 12.30pm on Tuesday.

Crews used foam to douse the flames before cutting away the metal outer casing to avoid the fire starting again and decanting most of the oil into another tank.

Over 20 square metres of insulation was destroyed by the fire and firefighters described the operation as a "painstaking" process.

Watch manager Keith Cunliffe said: "Initially it was flaming out of the top and then it was smouldering in the insulation. We were pulling out burning insulation all the time. It’s going to be expensive damage because of the nature of the beast."

He added that the incident could have been worse if workers hadn’t already been on the site to alert fire crews, but the danger was limited because the oil was contained within the tanks.

A spokesman for PDM said the blaze was not a major incident and would give no further comment.

Resident Marion Durkin, of nearby Walmsley Close, said residents could smell burning.

She said: "I came to the door and I could see a lot of smoke coming this way."