The fire broke out on Saturday at the Tata Electronics plant in Hosur, Tamil Nadu. No injuries were reported, as all employees present at the plant were safely evacuated.
The investigation is expected to delay the resumption of production at the facility, which employs around 1,500 workers.
It remains unclear whether the fire spread to nearby buildings, one of which is an iPhone assembly plant. Apple is accelerating the production and sales of iPhones in India to diversify its supply chain.