A consignment of suspected fake Islamic holy water has been seized from an Islamic bookshop at the start of Ramadan, Westminster City Council said.
Twelve bottles of what is thought to be fraudulent Zam Zam water were found in Westbourne Grove, west London.
The council has conducted a campaign against fake Zam Zam water which they say contains high levels of arsenic.
The water was seized after an anonymous tip-off and will be sent for tests to assess whether it poses a health risk.
The genuine water comes from the sacred well of Zam Zam in Mecca, the most holy city in Islam, and demand increases during Ramadan.
Westminster City Council said they were concerned that Muslims may be exploited and tricked into buying fake Zam Zam water during this period of high demand.
The council spokesman said the exploitation of people's faith for profit was "abhorrent."