South Essex: Deaths linked to drugs in five-mile radius
Four people within a five-mile (8km) radius have died in the past two days after taking drugs.
Essex Police is keeping an "open mind" as to whether the deaths in the south of the county are linked.
The force has not said what type of drugs were taken but warned against taking any illegal substances.
Det Ch Insp Stephen Jennings said: "At this stage it is not clear if these deaths are linked but we remain open-minded about that possibility.
"We believe the deaths are all related to the taking of illicit drugs. I would urge people not take any illegal substances at any time but particularly not at this time."
On Monday, a man in his 20s was found dead at an address in Leigh-on-Sea and a woman in her 30s died in Westcliff-on-Sea.
Since then, a man in his 40s has died at an address on Canvey Island and a man in his 20s was found dead in Benfleet.