While investigating cannabis grows, officers from Humberside Police, have noticed electricity is now being directly abstracted from the road.
Signs to look out for include unmarked vans with those completing the work also wearing unbranded protective wear such as hi-vis jackets and hard hats.
Police say they may ask residents to move their vehicle, or they might work extremely close to cars in order not to raise a direct concern.
There may also be late night activity at an address with items being removed.
The work will involve digging a hole and very quickly re-covering it as though nothing has happened.
Detective Inspector Tom Kelly said: “Whilst investigating these cannabis grows, we have noticed that electricity is often now being directly abstracted from the road.
“What this means is that those running the factories are digging up the roads, posing as legitimate workers, and then refilling the roads back in as if nothing has been done, once they have managed to tap into the power supply.
“Not only is the abstraction of electricity in this way incredibly dangerous for those living on the street, often these criminals are exploiting vulnerable people through modern day slavery to complete the work for them, which we won’t accept.
“I am appealing to you to get in touch with us at the earliest opportunity if you suspect this activity is taking place.”