The operation, which was conducted in partnership with the Driver and Vehicle Standards Agency (DVSA) and North Wales Police, targeted any vehicles carrying waste.
The DVSA and police stopped suspect vehicles with the aim of finding out if there was any waste on board and where it was due to end up.
Carys Williams, NRW team leader for industry and waste regulation in the North East, said: “By working in partnership with the DVSA and North Wales Police, we send out a positive message to those who seek to profit by breaking the law, that Natural Resources Wales will not tolerate any harm to North Wales communities or damage to the environment.
“Illegal waste carriers can have a detrimental effect on legitimate waste businesses that invest in the correct measures.
“Therefore, it is essential that we look to take action to protect people and the environment, as well as safeguarding the North Wales waste market.”
NRW says it undertakes regular operations such as this one across North Wales.
David Collings, the DVSA’s head of enforcement delivery, said his agency took part in the operation because its priority was to “protect everyone from unsafe drivers and vehicles”.
He added: “By working in partnership with other agencies we are able to pool our resources to help crack down on those flouting road safety rules and damaging the environment.
“We look forward to working with Natural Resources Wales and North Wales Police again and want to remind local vehicle operators of their duty to make sure their vehicles are well maintained and safely loaded to keep local Flintshire road users safe.”
NRW asked anyone who suspected there may be illegal waste activity in their area to contact them via their incident hotline on 0300 065 3000.
Last month, NRW asked the public to be “aware” of individuals and businesses advertising illegal waste collection services on social media (see letsrecycle.com story).
The Welsh regulator gave the public the average costs they might expect to pay for the proper collection of waste, including a figure of £52 for a car-boot sized amount.
Individuals who fail to meet their duty of care towards their waste could receive a fine if prosecuted, NRW warned.
NRW’s public register of approved waste carriers, brokers and dealers is available here.