Shanghai Volkswagen Automotive Co has launched an inspection into tires produced by Sumitomo Rubber Industries' China plants after claims by plant workers that sub-standard tires may be used in the new Passat.

China National Radio quoted plant workers as saying Sumitomo Rubber's Changshu plant in Jiangsu province used low grade materials between2011 and 2012, involving 17-inch and 18-inch mid- and high-end tires. The plant made tires for Dunlop China, and more than 1,100 allegedly sub-standard ones were produced in a single day, on Aug 2, 2012.

The Dunlop China plant is also inspecting the issue and will announce the outcome soon, according to a National Business Daily report on Thursday.

The report said the deputy head of the plant denied the use of low grade materials, but a company memo showed a meeting had decided a check into the matter was necessary.

"At the very least, even if the use happened, there won't be any safety hazard," Wu Xin, senior director of general affairs department at Sumitomo Rubber China was quoted as saying.

An industry insider told National Business Daily that there are differences between car and tire makers, so that a carmaker could hardly be involved in or supervise tire making.

Toyota, Nissan and Honda are also among major Dunlop customers.