Shipbuilding business in Sibu started in the 1930s to supply wooden boats for river and coastal navigation. It flourished in 1970s and 1980s along with increase in exports of tropical timber from Sarawak. It later shifted its focus into steel boat building. Some of the vessels in demand are tug boats for towing logs, barges for carrying logs, anchor handlers, Offshore Support Vessels (OSV), ferries, and express boats for carrying passengers. Most of the boats built are of small and medium in size. There are a total of 40 shipyards in Sibu. A majority of the workers are welders. In 2003, 17 of the shipyards were relocated to Rantau Panjang Integrated Shipyard Shipbuilding Industrial Zone, Sibu. This included Yong Chin Kui, Far East, and TuongAik. The boats built in Sibu are often exported to neighbouring state of Sabah, Peninsular Malaysia, Singapore, Indonesia and United Arab Emirates. In the year 1991, a total of US$50 million was earned for shipbuilding business in Sibu. In 2011, Sibu ship exports stood at RM 525 million. Sibu is also the only city in Sarawak to possess a vehicle assembly plant. The plant is operated by N.B. Heavy Industries Sdn. Bhd., and it has been assembling Ankai, BeiBen, Golden Dragon, Huanghai Bus and JAC commercial vehicles since 2010. Sibu has two industrial areas: Upper Lanang Industrial estate (Mixed Light Industries) and Rantau Panjang Ship Building Industrial Zone.