Police officers held a stop-and-search operation in London last week as the Environment Agency (EA) stepped up its fight against those who commit hazardous-waste crime.
A number of summons are to be issued after some of the vehicles pulled over were found to be carrying rubbish without the necessary licenses.
Warnings were sounded about an increase in hazardous waste dumping when co-disposal was banned by the Landfill Directive from July 16.
A spate of incidents have brought the crime back into the spotlight recently, with serial fly-tippers of hazardous waste being hunted in the two counties.
After believing it has caught the man responsible in Essex, the EA has also appealed for information on the dumping of 150 hazardous computer screens and pieces of medical equipment in villages around Chesterfield, Derbyshire.
The criminals involved in both cases could receive six-month prison sentences and £20,000 fines.
Since the ban on co-disposal slashed the capacity for hazardous waste, the EA has inspected more than 1,000 sites to keep a lid on fly-tipping.
EA chairman Sir John Harman said: We are determined to ensure that human health and the environment are not put at risk by criminals who flout the law.
That is why we have an extensive enforcement programme, which looks to take on the crooks dealing with hazardous waste from a number of angles.
Initiatives such as this send a message out to unscrupulous people who think they can make a quick buck at the expense of the environment we are coming after you.