Police on Tuesday broke up a sit-in by workers at the main plant of Yoosung Enterprise in Asan, South Korea, that was hampering production at most of the country's auto makers.

The 827,000-sq.-ft. (76,831 sq.-m) Asan facility is the largest of the six plants operated by Yoosung and produces a wide range of piston rings, cam shafts and other products. It is located adjacent to the company’s headquarters and employs less than 200 workers.

About 150 workers, reinforced by more than 300 unionists not employed by Yoosung, began occupying the plant over a collective bargaining agreement breakdown last Thursday.

This stopped delivery of piston rings, threatening operations at all five Korean auto makers. Hyundai and Kia had cut back production of engines and halted output of some of its vehicles on Friday and Monday. General Motors Korea also was forced to make some production adjustments.

More than 1,000 police entered the plant late Tuesday afternoon and by 6 p.m. local time the facility was cleared of strikers, according to news reports.

No violence or injuries were reported as a result of the police raid.

Yoosung says production operations may be normalized by Wednesday.