Muslims were warned today to avoid drinking bottled sacred water amid fears it could be contaminated with arsenic.
Leicestershire County Council said Zam Zam water, from Saudi Arabia, was likely to be illegal and could have high levels of arsenic as well as nitrates.
The council's Trading Standards Service warning comes just two days before Ramadan, the Islamic month of fasting, is due to start.
Genuine Zam Zam water, which is sacred to Muslims, comes from a specific source in Saudi Arabia and cannot legally be exported from that country for commercial sale. It can only be imported for personal use.
This means any product found in shops would have an uncertain origin and is likely to be illegal as well as possibly posing a safety risk, authorities said today.
Similar warnings have been issued by the Food Standards Agency and Trading Standards in previous years, again amid concerns over arsenic and nitrate levels in the water.
The penalty for selling false Zam Zam water is an unlimited fine or two years' imprisonment and traders can face a fine of £20,000 or six months' imprisonment for selling water which is not safe.
Leicestershire County Council head of trading standards David Bull said: "Food Standards Agency's tests have shown that some Zam Zam water sold in the UK, or brought into the UK for personal consumption, contains high levels of arsenic - almost three times the legal limit.
"Nitrates have also been found, which may increase the risk of cancer.
"Anyone who knows of Zam Zam water being sold in Leicestershire can report it to Trading Standards via Consumer Direct on 08454 040506."Reuse content