Police seized suspected class A drugs and a CS gas cannister in a raid on a house.
Officers targeted the house in Flamborough Road, Thurnby Lodge, Leicester, on Friday morning. A 22-year-old man was arrested at the scene.
Inspector Bill Knopp, commander of Spinney Hill Park police station, said a quantity of what it believed to be heroin was found in the house.
The substance has been sent for analysis.
Insp Knopp said: "We encourage people to tell us if they believe there is drug-dealing or drug misuse in their neighbourhoods to tell us about it and we will act on those concerns."