A probe into a district official by disciplinary authorities in Chongqing Municipality began Thursday after he was allegedly exposed in a sex video by a microblogger.

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 Sina Weibo, had not been modified.

However, the source said it has not yet been confirmed that the man in the video was Lei Zhengfu, a district official in Chongqing, as Ji claimed in his blog postings.

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 who looks like Lei having sex with a woman.

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

According to Ji, Lei, the incumbent secretary of the Beibei District Committee of the Communist Party of China (CPC), denied he was involved in the sex video, which was made 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 get 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 looking for corrupt officials everywhere."

Chinese netizens' zest for hunting down corrupt officials via the Internet has been boosted in recent years.

Xinhua