CHONGQING - A probe into a district official by disciplinary authorities in Southwest China's Chongqing Municipality began Thursday after he was allegedly exposed in a sex video by microbloggers on the Internet.

A government source confirmed that a preliminary investigation found the sex video posted by Ji Xuguang, who registered with his real name on China's twitter-like website of Sina Weibo, had not been modified.

However, the source said it was not yet confirmed whether the man in the video was Lei Zhengfu, a district official in Chongqing, as Ji claimed in his microblogs.

Ji, who identified himself as an investigative journalist on the website, uploaded seven microblogs, including the sex video on Tuesday night. It showed a man looking like Lei having sex with a woman.

Ji claimed that Lei kept an 18-year-old mistress.

According to Ji, Lei, incumbent secretary of the Beibei District Committee of the Communist Party of China (CPC), denied he was involved in the sex video, which was filmed in 2007.

He was then vice secretary of the district CPC committee. He claimed the video must have been "modified with photoshop software."

"Lei told me over the phone that he was willing to 'make friends' with me, when I called him to check his reaction," said Ji in one of his microblog messages.

Ji said he received an anonymous phone threat after he made contact with Lei over the phone.

Ji's microblogs have been forwarded on several popular Internet websites and forums. A microblogger coded "Tianjindewuliao" said "people are overlooking on corrupt officials everywhere."

Chinese netizens' morale in hunting down corrupt officials via the Internet has been boosted.

Web condemnation from the public led to the removal of safety official, Yang Dacai, from the northwestern Shaanxi province, in September, and urban management official, Cai bin, in southern Guangdong Province, in October.

The former was caught wearing different luxury watches in pictures posted on the Internet, while the latter was exposed to own 22 homes, far outpacing his salary.

Ji said the video and the details of Lei's scandal and corruption evidence was first exposed by a man called Zhu Ruifeng on media.people.com.cn.

Ji then investigated and called Lei to see his response, before forwarding Zhu's materials on his own microblog.

Ji added he had handed all the video material and other evidence on Lei's problem to Chongqing discipline investigators.

Previous probes into officials involved in sex scandals has often led to evidence of corruption. A tobacco official in Guangxi Zhuang Autonomous Region, Han Feng, was found guilty of corruption in 2010 after his diary detailing sexually explicit tales was posted online allegedly by one of his mistresses.

Calls to Lei by Xinhua went unanswered.