Holy drinking water contaminated with arsenic is being sold illegally to Muslims by UK shops, the BBC has found.
Zam Zam water is taken from a well in Mecca and is considered sacred to Muslims, but samples from the source suggested it held dangerous chemicals.
Tourists can bring back small amounts from Saudi Arabia, but it cannot be exported for commercial use.
An undercover researcher found large quantities of bottles being sold in east and south London, and in Luton.
The president of the Association of Public Analysts said he would "certainly would not recommend" drinking it.
A BBC investigation discovered Zam Zam water was being sold by Muslim bookshops in Wandsworth, south-west London, and Upton Park, east London, as well as in Luton, Bedfordshire.
"The water is poisonous, particularly because of the high levels of arsenic, which is a carcinogen," said Dr Duncan Campbell, president of the Association of Public Analysts.