Three contract workers died late Monday at Tata Electronics’ iPhone components factory in Hosur, Tamil Nadu, after reportedly being overcome by gas while servicing a water treatment tank run by Ecolab’s Nalco Water, Reuters reports. State officials, Tata and Apple are all expected to investigate, though production wasn’t affected since the site was shut for Diwali. Tata handles roughly 40% of India’s iPhone assembly, and the Hosur campus has faced a fire, a ransomware attack and pollution concerns in recent years.