Coca-Cola is to recall all bottles of its Dasani water in the UK, after levels of bromate were found to exceed legal levels.
Dasani is the second biggest selling bottled water in the US
The recall is an embarrassment for the drinks giant, which has faced criticism for selling what is treated and purified tap water.
Coca-Cola said it had consulted the Food Standards Agency, which agreed there were no immediate safety fears.
The recall of about 500,000 bottles is expected to be completed in 24 hours.
Coca-Cola produces Dasani from mains water at a factory in Sidcup, Kent.
The company says Dasani - recently launched in the UK - is "as pure as bottled water gets" thanks to a "highly sophisticated purification process".
Coca-Cola said the recall was a precaution.
One marketing expert said it could be costly.
"It's now going to be next to impossible for Coke to relaunch Dasani in the UK," said Allyson Stewart-Allen of International Marketing Partners.
"This is very surprising for a company as careful and deliberate as Coca-Cola, and a blow to the trust they're aiming to build with consumers as well as their strategy to diversify into drinks that can't be linked to obesity, such as water."
The Food Standards Agency describes bromate as "a chemical that could cause an increased cancer risk as a result of long-term exposure, although there is no immediate risk to public health".
In a statement, Coca-Cola said the contamination had been initially caused by its regular practice of adding calcium to Dasani, calcium which in this case "did not meet our quality standards".
As a result, bromate went on to be formed during the manufacturing processes.
"Immediately after we identified this issue we consulted with the Food Standards Agency," said Coca-Cola.
"The FSA has confirmed that there is no immediate health or safety issue. The withdrawal is a precautionary measure."
The firm added that the withdrawal only affected Dasani in the UK.
The UK limit for bromate in bottled and tap water is 10 parts per billion, while the Dasani samples had tested between 10 and 22 parts per billions, Reuters reported.
European tap water limits for bromate are less stringent at 25 parts per billion.
Thames Water, which supplies the Dasani factory, said the bromate had absolutely nothing to do with its mains water.
"Coca-Cola has indicated that the bromate was caused by its manufacturing process," said a Thames Water spokesman.
"We would like to reassure our customers that our water is regularly tested to the very highest standard."