Firefighters battled on Saturday to douse a fire that halted production at a major Tata Electronics plant in southern India which makes components for Apple’s iPhone, three people with knowledge of the situation said.

There were no reports of casualties, but it was not immediately clear how extensively the fire, near a building set to turn out complete smartphones soon, would disrupt operations of the plant in the city of Hosur in Tamil Nadu state.

Tata Electronics is one of the major contract makers of iPhones in India, along with Foxconn. The company said it was investigating the cause of the fire and would take necessary steps to safeguard employees and other stakeholders.

“There has been an unfortunate incident of fire,” a Tata Electronics spokesperson said in a statement. “Our emergency protocols at the plant ensured that all employees are safe.”

The fire caused the collapse of a building at the plant but no casualties were reported, a fire services official said.

“We can’t go inside now as the pathway is destroyed,” said J. Saravanan, a senior district official charged with handling industrial safety, adding, “It will take one day for it to cool down.”

Authorities were investigating the cause, he said.

Production was halted and employees were sent home for the day because of the fire, a person with direct knowledge of the incident said earlier, describing the blaze as chemical-related.

A second industry source aware of the plant’s operations said certain iPhone components were made at the affected building. However, the source added, it was not yet clear if a neighbouring building, where smartphone manufacturing was due to start by year-end, had also been affected.

With the facility inaccessible at the moment, the source said, an assessment of damage from the fire will have to be done later.

Apple made no immediate comment on the incident.

Firefighters will need time to extinguish the fire, which began in an area used to store chemicals, the fire official said on condition of anonymity, as he was not authorised to speak to the media.

More than 10 fire and rescue vehicles were fighting the flames, The Hindu newspaper said.