Ref. No. 39/1166
In the name of Allah the most Gracious the most merciful
The answer to your question is as follows:
Before declaring any food halal or haram we are obliged to know how the raw material for the food is procured and then how it is prepared in their kitchen. If the raw material is procured in a halal way and then the food is not fried in haram oil or there is no contamination with haram things, then it will be permissible and a Muslim can eat it. Otherwise it will be regarded Haram and one must avoid it. However, if you are not sure and you don’t know about the ingredients used in food, then it is preferable to refrain from eating in such restaurants.
And Allah knows best
Darul Uloom Waqf Deoband