Fire officers placed a 200m safety cordon around the plant as flames and a huge pall of smoke rose above the factory.
The blaze was confined to the biomass plant and took three hours to put out before the cooling-down process began with regular checks throughout yesterday. No-one was hurt.
Partial production resumed today and the company said it hoped to be running chipboard and lamination lines by the end of the week.
Sixty firefighters from across the north-east were called to the site. A full-scale investigation into the cause of the blaze was launched.
Fire officials are investigating early indications that thermal oil ignited and ruptured a pipe. "Thankfully there were no injuries," said managing director Bob Livesey. "All of our detection and safety systems worked extremely well and the fire service was able to bring the fire safely under control."
