Jubilant FoodWorks operates Domino's Pizza and Dunkin Donuts chains and Westlife Development runs McDonald's restaurants in west and south markets through its subsidiary.
The scrip of Jubilant Food tanked 12.35 per cent to Rs 975 while Westlife Development plunged 9 per cent to Rs 200 on BSE.
The stock of Britannia fell 2.6 per cent to Rs 2,611.20.
Bread samples of virtually all top brands in Delhi contained cancer-causing ingredients, a study released yesterday said, prompting the Union Health Ministry to order a probe.
The tested bread samples included brands such as Britannia, Harvest Gold and the fast food chains KFC, Pizza Hut, Domino's, Subway, McDonald's and Slice of Italy.
Britannia, KFC, McDonald's and Subway denied that these chemicals were used in their products. Other brands did not comment despite repeated attempts.