Warnings have been issued after two sudden deaths that may be linked to contaminated crack cocaine.
Police in Barnet, north London, said there have been two separate cases where men who took the drug died suddenly.
A 26-year-old man died shortly after taking the drug on January 20 in the Edgware area, and three days later a 48-year-old who was a crack user died suddenly from a heart attack in Friern Barnet.
Toxicology tests are being carried out but police have issued the warning as a precaution.
Chief Superintendent Adrian Usher said: "We would ask drug users to be very careful and strongly advise anyone who has recently bought crack cocaine to dispose of it immediately and seek immediate medical attention if they become unwell."
Anyone with information can call Barnet police on 101 and ask to speak to DC Mike Paton, or Crimestoppers anonymously on 0800 555 111.