MUMBAI -- After an epic legal row last year over suspected lead and undisclosed monosodium glutamate content in foreign noodles, India's latest health worry is carcinogenic dough.

A study by the Center for Science and Environment (CSE) has detected hazardous levels of a known carcinogen in 84% of bread sampled on sale in Delhi. The positive readings were for 1.15-22.54 parts per million of potassium bromate and potassium iodate, the former being a suspected carcinogenic chemical that has been banned globally.

"Products of Perfect Bread, Harvest Gold, and Britannia were those with higher levels," CSE said. The center said five top international fast food chains -- KFC, Subway, McDonald's, Pizza Hut, and Domino's Pizza -- were serving products, including burgers, pizzas, and sandwiches, that tested positive for the chemical.

It called for an immediate ban on these chemicals citing public health concerns. Their use in baking has been banned in many countries. Potassium bromate is a category 2B carcinogen -- meaning it is possibly carcinogenic to humans - while potassium iodate might trigger thyroid disorders.

CSE noted that in 1999, the World Health Organization's International Agency for Research on Cancer (IARC) classified potassium bromate as possibly carcinogenic to humans. The European Union, including the U.K., banned its use in 1990. Australia, Brazil, Canada, China, Colombia, New Zealand, Nigeria, Peru, and Sri Lanka all followed.

Seventeen years after the IARC study, the Food Safety and Standards Authority of India (FSSAI) has decided to remove potassium bromate from its list of permitted additives.

"A scientific panel had recommended removal of potassium bromate from the list of additives," Pawan Kumar Agarwal, FSSAI's chief executive, told the Press Trust of India. Kumar said the chemical has already been delisted as an acceptable additive, and notices will soon go out.

"As far as potassium iodate is concerned, we are examining the evidence and soon a decision will be taken," Kumar said.

The health ministry has ordered an official probe, but asked people not to panic.

Domino's brand operator in India, Jubilant Foodworks, said the company carries out regular assessment of the flour used in its bread to ensure compliance.

"We only use additives/ingredients duly permitted by the FSSAI in all our preparations," Jubilant said in response to clarifications sought by stock exchanges.

Shares in Jubilant Foodworks ended 4% lower at 1,066.50 rupees ($16) on the Bombay Stock Exchange during Tuesday's session, and Britannia ended down 1% at 2,652.55 rupees.

Last year, India's ban on Swiss conglomerate Nestle's Maggi instant noodles created a furore. FSSAI forced the removal of all nine Maggi instant noodle products in India after excessive lead was allegedly found in products. Traces of monosodium glutamate, a flavor enhancer, were also allegedly found, despite product labeling saying the noodles contained none.

Fallout from the noodle panic prompted Hindustan Unilever and Japan's Indo Nissin Foods to withdraw their competing products while Indian authorities probed the Nestle products, which were ultimately cleared after a court ordered independent testing.