Rumors are spreading quickly that radioactive materials were accidentally leaked from a state-of-the-art Chinese nuclear submarine moored in Dalian Port in Liaoning Province in the northeastern part of China.

The rumor was first reported on Saturday by Boxun.com, a website for overseas Chinese, before it was picked up by Sina Weibo, a Chinese microblogging site similar to Twitter.

Citing People's Liberation Army sources in Dalian, Boxun.com reported that there was an accidental leakage of radiation when engineers from a Chinese electronics company were installing equipment on the submarine.

Boxun reported that the accident happened suddenly, and that Chinese authorities had sealed off the area while an investigation was under way, while taking steps to ensure news of the accident did not spread.

The Chinese media and government have so far refrained from commenting on the rumors, which have stoked fears among netizens.

China possesses around 70 submarines. Six of them are nuclear-powered and five are part of the North Sea Fleet deployed around Bohai Bay. Only two Chinese nuclear submarine ports in the North Sea Fleet have been identified by outsiders. One is in Dalian and the other is in Qingdao.

In 2007, a U.S. spy satellite captured photos of a Chinese Jin-class nuclear submarine moored in Xiaopingdao, an island near Dalian. The submarine at the center of the latest rumor is a Jin-class nuclear sub, which measures 133 m in length and has a displacement of 8,000 tons. It is also equipped with intercontinental ballistic missiles with a range of 8,000 km. Two nuclear submarines have been commissioned so far, but three or four more are being made, according to military sources.

Chinese authorities earlier denied news reports that an oil leak had occurred on an offshore drilling platform in Bohai Bay in June, only admitting the leak one month later after netizens had already learned of the accident.

Boxun.com has often carried articles that are critical of Beijing, citing sources in China, as well as covering some sensitive issues that the Chinese media have been reluctant to handle. But it has also been known to make mistakes, with the latest being an erroneous report that former Chinese leader Jiang Zemin had died.