Cocaine users in Lancashire are being warned that the drug is being mixed with a painkiller which has been linked to kidney and liver cancer.
The chemical is known to have a numbing effect similar to cocaine
Police say the drug is being cut with the banned painkiller Phenacetin, which is used to bulk out the powder.
The chemical is known to have a numbing effect similar to cocaine, which makes it difficult for people to spot.
Officers have now warned pub and club owners to adopt a zero tolerance approach to drugs on their premises.
Supt Dave Brian from Lancashire Constabulary's Serious and Organised Crime Unit said: "The average purity of street cocaine used to be higher.
"We are now finding it to contain more of the harmful adulterants added by dealers in order to increase their profits."
"People shouldn't underestimate what impact taking cocaine, or any other drug, can have on their lives," he added.
"Not just on their health but socially, including debt, and also o their future employment as more and more employers are now carrying out drugs tests."