BEIJING (AP) — Foxconn Technology Group denied on Saturday that production was affected at a Chinese factory that makes Apple’s iPhones, although both state media and an overseas labor watch group said some workers halted production lines on Friday, apparently over higher quality control standards.

China Labor Watch, based in New York, reported that 3,000 to 4,000 workers at the Foxconn plant in Zhengzhou in central China went on strike Friday over increased quality control demands and having to work during an extended national holiday.

The state news agency Xinhua, quoting a spokesman for the management committee of the Xinzheng Comprehensive Bonded Area where the plant is, said some production lines were halted Friday when workers persuaded quality inspectors to skip work to show dissatisfaction over higher quality standards.

In a statement on Saturday, Foxconn, which is based in Taiwan, said production at the Zhengzhou plant continued without interruption. It denied any strike or work stoppage.