Apple iPhone maker Foxconn said on Thursday it is cautiously restarting production at its main plants in China and warned revenue will be hurt this year by the coronavirus epidemic.

Earlier ths week, Apple updated its March quarter sales guidance, saying factories in China have been slower to get back to work than first anticipated after Lunar New Year holidays were extended amid the outbreak.

Foxconn also said its plants in countries such as Vietnam, India and Mexico continue to operate at full capacity with expansion plans under way as it seeks to minimize the impact of the virus.

Research firm Canalys estimates Apple and Huawei, which is also a Foxconn client, have 99% of their production in China.

TrendForce has slashed its forecast for Apple’s iPhone production in the current quarter by 10% to 41 million units and warned it may revise down again by another 5-7% depending on how well factories in China ramp up production.