A British man has been stabbed to death in Peru after taking the hallucinogenic drink ayahuasca, police have said.
Unais Gomes is said to have been attacked during a shamanic ceremony, which involved drinking the plant brew, near the city of Iquitos.
A Canadian man, who was also taking part in the ritual, has been arrested. Reports suggested he may have acted in self-defence, police said.
The Foreign Office confirmed a British national had died in Peru on Wednesday.
The incident is said to have happened at Phoenix Ayahuasca, an alternative health centre in the Amazonian jungle.
It describes itself as a "safe and supportive place to experience plant medicines and explore the true nature of the self".
Witnesses told police that Canadian national Joshua Andrew Freeman Stevens, 29, stabbed Mr Gomes in self-defence, local police chief Normando Marques told Reuters.
Mr Gomes, thought to be 26, is alleged to have attacked the Canadian man with a knife from the health centre's kitchen before being stabbed with the same weapon, another police source told the agency.
A Foreign Office spokeswoman said: "We can confirm the death of a British national in Peru on 16 December 2015.
"We are in contact with the local authorities and stand ready to provide consular assistance to the family at this difficult time."
What is Ayahuasca?
Ayahuasca, also known as yage, is a blend of two plants - the ayahuasca vine and a shrub called chacruna, which contains the hallucinogenic drug dimethyltryptamine (DMT).
DMT - and therefore ayahuasca - is illegal in the UK, the US and many other countries.
Its effects include giving users a distorted view of objects or actual hallucinations. Scientific evidence of the clinical benefits of ayahuasca is limited but advocates say it has become increasingly popular as a tool to treat post-traumatic stress disorder (PTSD), depression, and addictions.
Ayahuasca could have serious implications for somebody who has a history of mental health problems, warns the Talk To Frank drug advice website. It can also trigger these problems in those who are predisposed, but unaware of it.