Smoke is seen from the explosion scene.

Death toll rose to 69 after a powerful blast ripped through a factory in Kunshan City of east China's Jiangsu Province on Saturday morning, injuring more than 150 others, government sources said.

Xinhua News Agency says the blast happened at around 7:37 a.m. inside a wheel hub polishing workshop owned by the Kunshan Zhongrong Metal Products Co., Ltd.

An initial probe indicated that the explosion might be caused by flames igniting dusts, the Ministry of Public Security said via its official weibo microblog site.

Officials are working on rescue efforts and providing medical treatment.

Five medical experts from Shanghai are on their way to the explosion site.

Kunshan govenrment also urged people to donate blood of all types at four blood-collection centers, the local government's media office said on Weibo.

State broadcaster CCTV showed footage shot by residents of large plumes of thick, black smoke rising from the plant. Several firefighting trucks were shown in the factory compound. News websites posted photos showing survivors or victims being lifted onto the back of large trucks, their bodies black presumably from burns or being covered in soot.

Some survivors were seen sitting on wooden cargo platforms on the road outside the factory, their clothes apparently burned off and skin exposed or being carried into ambulances.

Located about halfway between Shanghai to the east and Suzhou to the west, Kunshan city is the eastern gateway of Jiangsu province and was once known as "a town for fish and rice."