Businesses in Washington have been visited by the Environment Agency as part of a clampdown on pollution.
A team of eight officers attended 30 companies on the Swan Industrial Estates and the NEP Business Park last week.
They aimed to check the businesses store and remove waste in accordance with the law, and also carried out general pollution prevention inspections, looking at drainage, as well as waste and oil storage.
The officers identified a drain water pollution violation, a possible illegal waste site and a business that was illegally burning cardboard.
However, most companies were found to be complying with the law.
Environment officer, Katherine Dowling, who led the campaign, said: “It was a very useful and successful exercise.
"We’re working hard to raise awareness and ensure businesses are following their duty of care responsibilities, including making sure any waste they produce is handled responsibly and legally.
"This helps minimise the impact on communities and the environment that we all enjoy.
"It was pleasing to find that most businesses we visited are aware of and operating in line with the regulations.”
The Environment Agency regularly receives reports from nearby residents of noise, litter and odour from the industrial estate.
It is home to several waste operators, as well as businesses including metal works, fast food outlets, manufacturers, accident repair centres and IT centres.
The main focus of the patrol was on non-waste operators.
They officers were looking to assess each company's potential contribution to pollution in the area, and help them to reduce it.
Businesses were spoken to about rats, litter, noise and odour, and were given advice by officers.
The next stage of the process will see all of the businesses given a follow-up letter about their responsibilities under environmental legislation.
That includes ensuring their waste is collected by registered and licensed contractors with the correct paperwork.
Other follow up actions include writing to landlords and liaising with Sunderland City Council about fast food outlets.