Drug-users are being warned about a suspected bad batch of narcotics after two men were found dead surrounded by syringes and needles.
Police believe the men, who were in their 30s, had been using heroin.
One man was discovered in the garden of a house in Stockwell, south-west London, and another was found in a car park in Kennington, south-east London.
Det Insp Keith Richardson said the batch could pose an "immediate and lethal threat" to drug users.
'Immediate' threat
Officers were called after a body was found in the front garden of a house in St Michael's Road at 0800 GMT on Tuesday.
Shortly after 2100 GMT the same day the body of a man was found in an underground car park in Lollard Street.
Both men were found with syringes and other drugs paraphernalia close by.
Mr Richardson, said: "We are warning drugs users in Lambeth and the surrounding area to be especially careful.
"Drugs are always dangerous, but we are concerned that a particular batch currently in circulation may pose an immediate, lethal threat."
Police are still awaiting the results of post-mortem tests.