A Taiwan factory has fired three workers for playing the Facebook game Happy Farm during working hours, press reports said Friday.

Hanyale Industry Co, an auto parts factory in Changhwa, western Taiwan, sacked the three workers after catching them playing the Happy Farm game despite the plant management's warning against it, cable TV channel CTI reported.

"We have warned workers that during working hours, they cannot look at web sites unrelated to our work," manager Liao Wen-hsin said.

But the three workers plan to sue the factory, arguing that Happy Farm is not a sex video game and they were just relaxing.

Facebook, a social networking site, has been growing in popularity in Taiwan. Happy Farm is currently the most popular online game on the island, with some 3.3 million Taiwanese playing it, many during working hours.