DETROIT/HONG KONG - General Motors has approached previous potential bidders for its Hummer unit after a deal to sell the brand to an obscure Chinese firm collapsed, a source with knowledge of the matter said on Friday.

GM has reached out to the companies whose offers for the military-derived SUV line were turned down last year when the U.S. automaker agreed to sell Hummer to Sichuan Tengzhong Heavy Industrial Machinery, said the source, who declined to be identified because the discussions are private.

At least four Chinese companies were among the firms GM contacted to gage their interest in recent days, the source said, declining to give specific names.

Two had expressed interest in buying only part of Hummer's assets last year, such as tooling and equipment at GM's Hummer plant in Shreveport, Lousiana, the source said. The other two had made offers for the brand.

The No.1 U.S. automaker said on Wednesday it would shut down Hummer after Tengzhong's $150 million bid to buy the money-losing brand collapsed, reportedly due to opposition from Chinese regulators. At that time GM said it would continue to entertain viable offers early in the wind-down process.

(Reporting by Soyoung Kim and Doug Young; Editing by Jacqueline Wong)