Muslims have been warned water supposedly drawn from a well in Mecca could have high levels of arsenic.
Yunus Sidat is no longer selling the water
Trading Standards officers tested bottled Zamzam "holy water" at a number of outlets in the UK and some of them failed water quality tests.
Brian Johnson of Leicester Trading Standards said: "We found levels of nitrates at three times the legal limits and arsenic at twice the limit."
Shopkeeper Yunus Sidat said he has stopped selling the water at his shop.
Trading Standards officers said people couldn't be sure the water had come from Mecca.
"There is a demand during Ramadan because people like to break the fast with dates and Zamzam water," said Mr Sidat.
"I don't want to deal with something that is not really Zamzam water."
Arsenic can cause cancer if consumed over a long period of time and nitrates can cause heart problems, Brian Johnson said.
A Trading Standards statement said: "As genuine Zamzam water cannot be legally exported from Saudi Arabia for commercial sale, any product found in the shops would have an uncertain provenance and pose a possible safety risk."
Sheikh Ibrahim Mogra, who has served the Muslim Community in Leicester for 16 years, said people should use Zamzam water if brought from Mecca by friends or relatives, but any bottled Zamzam water from a shop should be avoided.
The Zamzam well is located in Makkah, at the heart of the Hajj pilgrimage, a few metres east of the Ka'bah.