Chinese workers at a construction site in Brazil for a factory owned by China's electric vehicle producer BYD are victims of human trafficking, Brazilian labor authorities said on Thursday in a growing controversy in BYD's biggest overseas market.

Authorities in Brazil said Friday they are probing Chinese auto giant BYD and one of its contractors for suspected "trafficking" of Chinese workers building a factory in the South American country.

BYD has been building the factory with an annual capacity of producing 150,000 cars initially in Brazil, the Chinese EV giant's largest overseas market, as part of plans to start production there.