The chief executive of the Environmental Agency has visited the site of the former Alex Smiles fire as work continues to put out the blaze.
The blaze broke out at the Deptford compound on Monday evening, with the smoke caused by the incident leading to a warning living and working near to the site.
This morning, 18 firefighters from Tyne and Wear Fire and Rescue remain on the site and are using jets and a high volume pump.
James Bevan, chief executive of the Environment Agency, visited the scene yesterday as officers from his organisation work alongside Sunderland City Council and the fire service to deal with the incident.
He said: "I have been here to talk to the local Environment Agency team, who are doing fantastic work to manage the risks to the environment and to the public health, and to talk to the fire and rescue service and local authorities and the Salvation Army too, who are there to help.
"It's been really inspirational to see the team spirit that exists right across the board to do everything we can, not just the Environment Agency, but all those agencies, the fire service, the local authority, to manage the risks and go the extra mile for the people that we are here to serve."
A huge plume of black smoke was sent up into the air by the blaze as it began, making it visible for miles.