Two young Devon men have died after taking drugs in Amsterdam.
The unnamed men, aged 20 and 21, were found in a hotel in the Netherlands after they snorted what is believed to have been white heroin on Tuesday.
The Foreign Office said it is in contact with Dutch authorities and is "providing consular assistance to the family".
Dutch police spokesman Rob van der Veen confirmed the two men are from Devon, and said their bodies were found beside traces of a white powder believed to be white heroin - a type of heroin spiked with powerful painkillers.
"We did a quick test to find out what kind of powder it was. It wasn't cocaine, it was an opiate - in this case, white heroin," Mr van der Veen said.
"We took the sample to the Dutch forensic institute and they found out that the contents of this material is the same contents as other material that we already seized in other cases where people got sick," he added.
Investigators believe the men were targeted by the same dealers linked to the death of another Briton last month.
Authorities in the area are urging tourists not to buy drugs from street sellers.
Pamphlets handed out to tourists warn: "The last couple of weeks several tourists were hospitalised with severe health problems after using cocaine bought on the street ... Research has revealed that the cocaine used was not cocaine but white heroin."
Later this week, a post-mortem examination will confirm the time and cause of the deaths
