BENGALURU (Reuters) - Extensive damage from a fire at Tata Group's Apple iPhone component plant in southern India could hamper production ahead of a festive season sales surge, an industry watcher and a source said, forcing the U.S. firm's suppliers to arrange critical parts from China or elsewhere. The weekend blaze has caused an indefinite production halt at Tata's Hosur plant in Tamil Nadu, the only Indian supplier of iPhone back panels and some other parts for both contract manufacturer Foxconn in the country and its own iPhone assembly at another plant. Hong Kong-based Counterpoint Research told Reuters it estimates local sales of 1.5 million units of iPhone 14 and 15 models during the Indian festive season which runs from late October to early November, with Apple struggling to fulfil as much as 15% of that demand due to the fire. "There will be a 10-15% impact on production of older iPhone models from India.