TAIYUAN - A police officer in Taiyuan City, capital of north China's Shanxi Province, is under investigation for allegedly beating a woman.

A picture showing the police officer, surnamed Wang, supposedly beating a female migrant worker in front of a construction site has circulated widely on China's twitter-like Sina Weibo.

The woman, 47-year-old Zhou Xiuyun from Zhoukou City in Henan Province, was later found dead.

Her son Wang Kuilin told Xinhua that 13 people from his hometown have worked in a construction site in Taiyuan since mid October. But the boss delayed payment of their 29,000 yuan (about 4,700 US dollars) salary.

As the Spring Festival, or the Chinese New Year, will be celebrated soon, the migrant workers planned to ask for their money and return home to celebrate the festival.

On December 13, Wang Kuilin and three other workers came to the construction site, but were stopped by the guard who later called police, Wang said.

Wang's parents were worried about their son and also came to the site. His father was pressed down to the ground by police. A police officer also surnamed Wang pulled his mother's hair and twisted her neck, the son said.

"My mom lied on the ground for nearly one hour, and another police officer trod on her hair and accused her of playing dead," he recalled.

Later on, Wang Kuilin and his parents were all brought to the police station. He said he was not sure whether his mother was beaten to death at the site or later at the police station.

Local police said further investigation is under way.

Salary delays have been a perennial headache for hundreds of millions of migrant workers, who often lack formal contracts and sometimes go unpaid after their companies report low earnings or declare bankruptcy.