The Health and Safety Executive has launched an investigation into a wood recycling plant after a week-long fire.

Sonae, in Knowsley Industrial Estate, Kirby, has come under the spotlight after 60 firefighters were called to battle a large blaze involving 2,000 tonnes of woodchip.

The fire, which started around 8pm on 9 June, burned for four days and firefighting operations were scaled down on 14 June. The site is still being checked regularly.

It involved six large storage hoppers made of concrete. Firefighters managed to contain the flames so that the fire did not spread. There were some “small explosions” from a conveyor belt, Merseyside Fire and Rescue Service said.

Due to fears about the safety of the concrete bunkers, firefighters had to tackle the fire from the outside with a controlled burn out. The 'extensive quantity' of material involved also contributed to difficulties.

Speaking last week, group manager Guy Keen said: “Difficulty in accessing the extensive quantity of material and the need to minimise the impact to the environment have limited the tactical options...

“We are on track to conclude fire service operations by the end of the week. Most of the product has burnt off. The trouble we have is that the concrete bunkers are unsafe for firefighters to deal with the fire from the inside, so we have been carrying out a controlled burn out to minimize the smoke and impact on the environment.

“Out of the six bunkers involved in the fire, four have no or very little product remaining and the other two have low to moderate product that is still smouldering.

He confirmed that Sonae was looking to start demolition of the bunkers early next week, following a recommendation from the fire service and approval from Knowsely Council.

Sonae Industria (UK) Limited has been prosecuted a number of times by HSE for breaches of the Health and Safety at Work Act 1974. Following the latest incident, Knowsley MP George Howarth has called for the plant’s closure.