About 50 workers unhappy about pay at a Toyota parts supplier in north China's Tianjin refused to work Thursday but the plant's operation was not affected, local authorities said Thursday.

This was the second strike hitting auto parts suppliers for Toyota's assembly plants in the port city this week.

About 50 workers of Toyota Gosei (Tianjin) Co. (TG) refused to work, demanding higher pay, a government official at the administrative committee of Dongli Economic Development Area, said on condition of anonymity.

"Four teams of local officials and company managers are negotiating with the workers," the official said.

The plant in Dongli Economic Development Area, where more than 30 Toyota suppliers are sited, has more than 1,300 workers with an average monthly wage of about 1,500 yuan (220 U.S. dollars).

Workers planned and called for the strike early June on the Internet. The company had agreed to raise the workers' wages by 17 percent before the strike, the official said.

Usually the company raises wages by 15 percent every year, he added.

TG, established in 1995 with a registered capital of 200 million yuan, had an annual sales revenue of 1.53 billion yuan in 2009.

Tianjin Star Light Rubber & Plastic Co. (Star Light), a TG subsidiary in Tianjin's Xiqing Economic Development Area, was hit by a strike Tuesday.

More than 1,000 workers joined the one-day strike, demanding their pay go back up to 2009 levels.

On average, the workers' pay had dropped by 50 percent since early 2010, said a woman employee surnamed Huang.

The workers stopped striking after the company agreed to their demands Tuesday night, said a worker surnamed Cai.

The walkout had not disrupted Star Light's supply to Toyota's assembly lines in Tianjin, a Tianjin Toyota spokesman surnamed Bi said, stressing Toyota was not involved in Star Light's operations.

TG and Star Light declined to comment on the strike and tightened security at the plants' gates.

The strikes at TG came after a string of walkouts over pay in China since early May: three at Honda's auto parts plants in Guangdong, one at a parts supplier in eastern China's Jiangsu Province and another at an industrial sewing machine company, also funded by a Japanese investor, in Xi'an, capital city of northwestern China's Shaanxi Province.