Hyundai Motor’s labor union launched a full-day strike Friday, halting production at the automaker’s major South Korean plants as negotiations over wages and working conditions remained deadlocked.

The walkout was the first since 2016 in which members of the Hyundai Motor branch of the Korea Metal Workers’ Union staged an eight-hour strike for each shift, the Korea Herald reported.

Production was suspended at plants in Ulsan, Asan in South Chungcheong Province and Jeonju in North Jeolla Province, with both morning and afternoon shifts staying off work.

Around 39,000 union members participated, including production and office workers.

The union has staged partial strikes since wage negotiations began on May 6. Industry estimates suggest the disruptions have resulted in production losses of about 55,200 vehicles, equivalent to more than 2.3 trillion won ($1.66 billion) in potential sales.

Additional four-hour strikes are planned for Monday and Tuesday.

Negotiations resumed Monday after a break of more than 40 days but again ended without an agreement.

The two sides remain divided over wages, reinstatement of dismissed workers and extending the retirement age. The union is also seeking employment protections related to artificial intelligence, a shorter workweek and higher bonuses.