Many people observing this month of Ramadan might come across a few promotions for Zam Zam water.

But beware, as the Food Standards Agency is advising consumers in the UK to keep an eye out for the fraudulent sale of Zam Zam water which may contain high levels of arsenic. A brand of Zam Zam formally sampled by the London Borough of Westminster has been found to contain almost three times the permitted level of arsenic, which could contribute to increasing people's risk of cancer. Zam Zam water can be found on sale throughout the year, but sales are more frequent around Ramadan.

Zam Zam water, which is sacred to Muslims, comes from a specific source in Saudi Arabia and cannot legally be exported from the country for commercial sale and can only be imported for personal use.