SHANGHAI, May 21 (Reuters) - China's Shanghai Stock Exchange said on Tuesday it was looking into trading of Nanjing Chemical Fibre shares after their abnormal price swings raised concerns about potential market manipulation.

Shares of the fibre producer, which were up 10% at 8.34 yuan on Monday, tumbled to 6.82 yuan at 14:36 p.m. (2236 GMT) - roughly the time a social media post gave in its prediction of such price move - to finish the day down 10%.

The Shanghai exchange spotted online information related to the moves in the company's shares on Monday and immediately initiated scrutiny over the transaction, the bourse said in a statement.

"(Nanjing Chemical Fibre's stock) will give you a surprise at 14:34," said a user on financial platform Hithink RoyalFlush Information Network Co before the price slump in a post seen by Reuters.

The company had closed up 10% by the daily upper limit for six consecutive days before Monday's slump, and it finished up 10% again on Tuesday.

"The company's production and operation conditions are normal and no major changes have occurred," Nanjing Chemical Fibre said in a statement following the regulator's announcement.

"In view of the recent large fluctuations in the company's stock price, there may be irrational speculation," the company said.

China's securities regulator vowed in March to crack down on market misbehaviour such as market manipulation and insider trading to restore confidence in the stock market after a punishing three-year slump.

(Reporting by Shanghai Newsroom Editing by Tomasz Janowski)